Unusual Orbits for Unusual Missions

by | Oct 5, 2015 | Advanced Rocketry | 100 comments

Our choice of orbits can create scientifically useful space missions that can be operated at lower cost than their more conventional counterparts. How this has been done and the kind of missions it could enable in the future is the subject of James Jason Wentworth’s essay. An amateur astronomer and interstellar travel enthusiast, Wentworth worked at the Miami Space Transit Planetarium and volunteered at the Weintraub Observatory atop the adjacent Miami Museum of Science. Now making his home in Fairbanks (AK), he was the historian for the Poker Flat Research Range sounding rocket launch facility. His space history and advocacy articles have appeared in Quest: The History of Spaceflight magazine and Space News.

by J. Jason Wentworth

In the 1990s, then NASA Administrator Daniel S. Goldin introduced the “Better, Faster, Cheaper” paradigm for space missions. While NASA’s subsequent experiences led many engineers to modify that to “Better, Faster, Cheaper–choose two,” the goal of low cost has remained a primary goal for space mission planners. One way to reduce the cost of a mission is to select a trajectory that requires the least possible change of velocity (called Delta-V by engineers and orbital dynamicists) to achieve the mission’s objectives. This requires less propellant aboard the spacecraft, which results in a smaller and lighter spacecraft, which in turn can usually be lofted by a smaller and less expensive launch vehicle. (Very high-energy missions such as New Horizons are exceptions. In such cases, launching the smallest possible spacecraft merely makes such missions possible within a practical flight duration–even when using the most powerful launch vehicles available–because the velocities required for even the lowest-energy trajectories are so high.)

Another factor that affects the spacecraft’s required amount of onboard propellant is the stability of the mission orbit. If frequent orbital adjustments are necessary for any reason, a larger propellant reserve will be required, which will bump up the probe’s size and mass. The type of spacecraft stabilization system that is used also has an influence on the propellant reserve. A three-axis stabilized probe in orbit around the Moon, the Sun, another planet, or any other body will require more thruster firings (to point its sensors and imaging system at its target body, and to aim its high-gain antenna at Earth) than will a spin-stabilized spacecraft, so the latter can operate for many years using very little propellant for attitude control.

The spin-stabilized Pioneer spacecraft all exhibited this characteristic of very long life. Perhaps the most impressive of the series (besides the Sun-orbiting Pioneer 6 – 9 interplanetary probes, which lasted for multiple decades; two of them may still be functioning) was the Pioneer Venus Orbiter, which returned images of and data on the planet (and Comet Halley) for nearly 14 years, in the hostile thermal and solar radiation environment around Venus. [1] In March of 1986 Pioneer 7 also flew within 12.3 million kilometers (7.6 million miles) of Halley’s Comet and monitored the interaction between the cometary hydrogen tail and the solar wind. It discovered He+ plasma produced by charge exchange of solar wind He++ with neutral cometary material. [2]

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Image: Orbit attitude of Pioneer Venus 1 between 1978 – 1980 and 1992. Credit: NASA/Ames.

Since the space age began, other trajectories besides the classical Hohmann transfer ellipse have been devised to get satellites and space probes to their destination orbits or worlds. These are used to minimize the necessary Delta-V, or to optimize planet arrival times, or both. Some geosynchronous satellites are now first injected into “super-synchronous” transfer orbits from their initial low-altitude parking orbits, from which they are later maneuvered downward into their 24-hour operational orbits. The Pioneer Venus Orbiter traveled along a similar path to Venus; it was boosted from its parking orbit around the Earth into a solar orbit that initially passed outside the Earth’s orbit about the Sun before curving inward to intercept Venus in its orbit.

Other unusual types of orbits exist, some of which were discovered when asteroids were found to be moving in them, and they are also useful for low-Delta-V (and thus lower cost) space missions. The best-known ones are halo orbits and the tadpole-shaped Lissajous orbits, in which several spacecraft have traveled around the Sun-Earth L1 and L2 Lagrangian points and the Earth-Moon L1 and L2 points.

Enter the Horseshoe Orbit

A more recently-discovered path (which a 2011 Centauri Dreams article, Stable Orbit for a Newly Discovered Companion, discusses) is the horseshoe orbit, which got its name from its shape. [3] A small object in such an orbit goes around the Sun in a normal, low-eccentricity (close to circular) elliptical orbit in the direct (prograde) direction, but since its orbit has nearly the same period and shape as the orbit of a nearby planet (Earth, in the case of the horseshoe-orbiting asteroids discovered to date), gravitational interactions with Earth create the horseshoe path (which occurs only in the Earth-centered reference frame, as the asteroid orbits around the Sun normally). This celestial “dance” works as follows:

As the asteroid is about to pass the Earth in its slightly lower, more rapid orbit, the Earth’s gravity pulls it toward itself; this speeds up the asteroid, which causes it to move farther from the Sun (and thus into a higher orbit), and this then causes the asteroid to slow down, because objects in higher orbits move more slowly. In its higher, slower orbit, the asteroid then begins to drop behind the Earth, slowly “drifting” backwards all the way around the Sun (from the Earth’s perspective–the asteroid is orbiting the Sun in the same direct [prograde] direction as Earth, just more slowly). Many years later, as the asteroid again approaches Earth (from ahead of our planet this time), the Earth’s gravity slows down the asteroid, which causes it to fall into a lower, faster orbit around the Sun. Now moving faster than the Earth (inside Earth’s orbit), the asteroid slowly “drifts” all the way around the Sun again (moving forward this time, from Earth’s perspective), after which it repeats the whole horseshoe orbit cycle again. [4]

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Image: A horseshoe orbit, showing possible orbits along gravitational contours. In this image, the Earth (and the whole image with it) is rotating counterclockwise around the Sun. Credit: Wikimedia Commons.

While other asteroids in horseshoe orbits with respect to Earth have been found before, their orbits aren’t long-term stable. Within a certain range of distances, orbital eccentricities, and velocities, however, stable horseshoe orbits are possible, and the asteroid 2010 SO16 (the subject of the Centauri Dreams article in Reference 3) is in one, having possibly followed its current orbit for up to two million years. In addition, it is possible–as 2010 SO16 might have done, as is mentioned in the article–for asteroids (or other objects, such as spacecraft) to librate (migrate) from Lissajous orbits around the Sun-Earth L4 or L5 Lagrangian points into stable horseshoe orbits. Migration from a horseshoe orbit back into a Lissajous orbit might also be possible, and what an unpowered asteroid could do, a self-powered space probe could likely also do–using little propellant.

Another unusual kind of orbit is the quasi-satellite orbit, in which NEAs (Near-Earth Asteroids) have also been discovered. [5] A quasi-satellite is in an orbit around the Sun that has a 1:1 resonance with the orbit of a particular planet. This causes the quasi-satellite to stay close to that planet over many orbital periods. A quasi-satellite’s orbit has the same period as the planet’s orbit, but the quasi-satellite’s orbit has a different–usually greater–eccentricity than the planet’s orbit. As observed from the planet, the quasi-satellite appears to move in an oblong retrograde loop around the planet, although both bodies are orbiting the Sun in direct (prograde) orbits.

Orbital Dynamics and ‘Fuzzy Boundaries’

Pioneer-6-9

Pioneer E (which would have been named Pioneer 10 if it had not been lost in its failed launch on August 27, 1969) was the fifth and last of the series of solar-powered, drum-shaped Sun-monitoring interplanetary probes that began with Pioneer 6 in December of 1965, and Pioneer E was intended to orbit the Sun as a quasi-satellite of Earth. Had it reached its planned solar orbit, Pioneer E (which was launched–and lost–with the TETR C test and training satellite, the intended third “practice” satellite for the Apollo tracking and communications network) would have passed inside and outside the Earth’s orbit, alternately speeding up and slowing down relative to Earth. This would have kept Pioneer E within 16 million kilometers (10 million miles) of Earth during the spacecraft’s design lifetime of from six months to two and one-half years. [6] (It would likely have operated for much longer than two and one-half years, as its sister probes Pioneer 6 – 9 demonstrated.)

Image: Artist’s conception of the Pioneer 6-9 spacecraft. Credit: NASA.

Orbit changes could be done using even less propellant (virtually none, in some cases) by employing Dr. Edward Belbruno’s principle of gravitational “Fuzzy Boundaries,” which involve the physics of chaos. [7, 8, and 9] This was first demonstrated in 1991 after Japan’s first lunar probe, the combined Hiten/Hagoromo spacecraft, ran into difficulties. Launched on January 24, 1990, the craft was injected into a highly-eccentric elliptical Earth orbit that passed beyond the Moon. The tiny Hagoromo lunar orbiter separated from Hiten during its first lunar swing-by and fired its solid propellant retro-rocket as the vehicles passed the Moon; while Hagoromo entered lunar orbit as intended, its radio transmitter failed when its retro-rocket fired (optical telescopic observation from Earth confirmed its entry into lunar orbit), which rendered it scientifically useless. [10] On March 19, 1991, Hiten performed the first-ever aerobraking maneuver, skimming the Earth’s atmosphere to change its orbit.

Having learned of Hagoromo’s transmitter failure, Edward Belbruno approached ISAS (the Institute of Space and Aeronautical Science) and offered to help them get their still-functioning Hiten lunar flyby spacecraft into lunar orbit. The probe, which was in a highly-eccentric Earth orbit, was moving much too fast during its lunar flybys to brake into lunar orbit using its onboard propellant. But by utilizing his “Fuzzy Boundaries” method, which involved using the combined gravity of the Moon and the Earth, on October 2, 1991 Hiten’s flight controllers were able to maneuver the probe into a preliminary, temporary lunar orbit using almost no propellant. After that, Hiten was targeted to fly through the Earth-Moon L4 and L5 points to collect data on any meteoric dust that was thought to possibly have accumulated there (none was detected). On February 15, 1993, Hiten was directed into a permanent lunar orbit, where it remained until it was deliberately crashed on the lunar surface on April 10. [11]

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Image: An artist’s conception of the Hiten spacecraft. Credit: JAXA.

A Panoply of Applications

Stable horseshoe solar orbits and quasi-satellite solar orbits–entered and/or exited with the aid of Dr. Belbruno’s “Fuzzy Boundaries” method, making use of planetary as well as solar gravity–would be useful for Pioneer 6 – E type solar monitoring probes, which could observe portions of the Sun that cannot be seen (at any given time) from Earth. They could also, in concert with solar observations from Earth (or from Earth satellites), make stereo observations of solar features at many places along their horseshoe or quasi-satellite orbits. These same solar probes could also, as the Sun-orbiting Pioneer 7 interplanetary probe did, encounter and examine comets that pass through or near their orbits (flybys of asteroids that pass them would also be possible). If necessary, such probes could modify their horseshoe or quasi-satellite orbits (speeding up or slowing down, as needed) in order to make closer flybys of comets and asteroids (and later return to their original orbits) using very little propellant. Or, the probes could utilize solar sail propulsion (a simplified heliogyro sail should work nicely) to make such orbit changes, using no propellant at all.

Another application for horseshoe and quasi-satellite solar orbits would be to place NEO (Near-Earth Object) space telescopes in such orbits, much closer to the Sun than Earth’s distance. These locations would enable the spacecraft to see Earth-crossing NEOs whose orbits keep them mostly inside Earth’s orbit, and objects that could become dangerous to Earth in the future (via gravitational encounters with Venus and/or Mercury) would also be visible to these spacecraft. (To telescopes on or near the Earth, the sunlit sides of these small, often dark-colored objects face away from our planet, making them virtually impossible to see in the Sun’s glare, and Earth-based telescopes could never search for them in a truly dark sky because they would never be far from the Sun.) The B612 Foundation and its aerospace industry partner Ball Aerospace plan to send their NEO-seeking Sentinel space telescope to a Venus-like solar orbit for this reason. [12 and 13]. A horseshoe orbit or a quasi-satellite orbit “threaded around” Venus’ orbit about the Sun could reduce the necessary Delta-V (and thus the spacecraft’s launch vehicle and onboard propellant requirements) by utilizing Venus’ gravity to help establish–and later maintain by itself–either type of orbit for the Sentinel spacecraft.

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Image: The Sentinel Space Telescope, being built by the B612 Foundation. Credit: B612Julie (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons.

Closer to home, Earth-centered horseshoe orbits–in which evenly-spaced communication, weather, or Earth resources satellites could “cycle” around the Earth as if on a circular conveyor belt (with two sets of spacecraft, on the inner and outer edges of the “belt”)–could provide global coverage not only of Earth, but they could also serve as communication relays for the lunar farside and for the Earth-Moon L2 point behind the Moon. (For circum-terrestrial horseshoe orbits, the Moon’s gravity would serve the same function that the Earth’s gravity does for Sun-centered horseshoe orbits that are “threaded around” Earth’s orbit about the Sun.) They could also provide close-up lunar observation to monitor time-variant lunar phenomena (the lunar “dustosphere’s” monthly cycling under the influence of Earth’s magnetotail, lunar meteorite impacts during meteor showers, TLP [the luminous Transient Lunar Phenomena], etc.).

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Surprisingly, even low-cost suborbital interplanetary missions are possible. In addition to gathering data on the time-variant phenomena of the interplanetary environment, they could also collect dust, ice, and gas samples from comets that pass relatively close to Earth. NASA’s simple, inexpensive solid propellant Scout satellite launch vehicle, manufactured by LTV (Ling-Temco-Vought) using existing “off-the-shelf” rocket motors, was also used for several high-altitude suborbital probe missions that reached tens of thousands of kilometers into space. [14] (A rocket that ascends to an altitude of one Earth radius or higher is considered a space probe rather than a sounding rocket, because reaching one Earth radius requires a rocket velocity that is equal to Low Earth Orbit [LEO] orbital velocity.) The U.S. Air Force’s Blue Scout vehicles (which were similar to the NASA Scout vehicles for the most part, but were somewhat different because they were produced by a different contractor, the Ford Motor Company’s Aeronutronic Division) also flew numerous probe missions. [15 and 16] One in particular, a Blue Scout Junior launched from Cape Canaveral on August 17, 1961, reached an altitude of 225,000 kilometers (140,000 miles)–more than halfway to the Moon–on a suborbital flight lasting days. Unfortunately, the payload’s transmitter failed during the final (fourth) stage’s burn, rendering the flight scientifically useless. [17 and 18]

Image: The Blue Scout Junior. Credit: Peter Alway/Encyclopedia Astronautica: http://www.astronautix.com/index.html.

In his 1957 book The Making of a Moon: The Story of the Earth Satellite Program (and in its 1958 post-Sputnik revised second edition), Arthur C. Clarke pointed out that by launching suborbital vehicles at velocities approaching Earth’s escape velocity, their payloads could reach altitudes of millions of miles before falling back to Earth. [19] Interestingly, the altitudes achieved begin to increase dramatically at only 35,000 kilometers per hour (22,000 miles per hour), significantly below Earth’s escape velocity. As he wrote: “A rocket launched vertically at 22,000 miles an hour–or four thousand miles an hour faster than a satellite–would reach an altitude of about fifteen thousand miles before gravity checked its speed and it fell back to Earth. Slight further increases in velocity would give altitudes of millions of miles, until at the critical speed of 25,000 miles an hour the rocket never came back at all.”

Such vehicles could be very small–the 7.3-meter (24-foot) long, balloon-launched Project Farside probe rockets of the late 1950s, which reached nearly orbital velocity and rose to altitudes of between 3,200 and 5,000 kilometers (2,000 and 3,100 miles) with 1.4 to 3.3 kilogram (3 to 5 pound) payloads, could have reached the vicinity of the Moon with the addition of a fifth stage, which was proposed. [20] But this proposal was not proceeded with, possibly because the electronics technology of those days likely wouldn’t have enabled such small payloads to return meaningful data from the Moon’s distance (the frequent failures of the Farside vehicles’ payload transmitters also didn’t encourage much confidence in more ambitious ventures). But today a full suite of instruments, an S-band or X-band telemetry transmitter, and their solar cell or battery power supply could be accommodated in payloads of that mass range.

farside

Image: Working on Project Farside. Credit: Parsch, Directory of U.S. Military Rockets and Missiles: http://www.designation-systems.net/dusrm/app4/farside.html.

Existing high-performance multi-stage sounding rockets could, if topped with multiple high-velocity stages, boost heavier payloads to such velocities (similar vehicles have boosted artificial meteors to velocities far in excess of escape velocity, beginning in 1957). [21 and 22] Such “souped-up” sounding rockets, or small–particularly air-launched satellite launch vehicles with additional upper stages, such as Orbital Sciences Corporation’s Pegasus XL and the upcoming Boeing ALASA (Airborne Launch Assist Space Access) system–could loft small suborbital interplanetary probes. [23 and 24] This capability would make possible low-cost, rapid comet sample return missions to “targets of opportunity,” comets such as IRAS-Araki-Alcock and Hyakutake that pass within a few million kilometers of Earth.

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Image: The Pegasus XL launch vehicle operated by Orbital Sciences Corporation. Credit: NASA.

The recoverable portion of the spacecraft could use a deployable aerogel particle collector that would be housed in a small, blunt re-entry heat shield similar to that of the Pioneer Venus Small Probes or the Japanese Hayabusa and Hayabusa 2 asteroid sample return probes. The expendable section of the spacecraft, which would burn up upon re-entry into the Earth’s atmosphere, would carry fields and particles instruments and an imaging system. At other times, such suborbital probes could collect intact meteoroids from meteor shower streams for return to Earth, and/or they could gather data on the far regions of Earth’s magnetosphere and magnetotail, including their interactions with the solar wind and the solar magnetic field. Since the parent bodies of many meteor shower streams are now known (most originate from comets–a few are from asteroids), suborbital probes would offer inexpensive, frequent, and regular opportunities for collecting samples of these objects.

By substituting subtlety and cleverness for brute force, and by letting some mission targets come to their probes more than vice-versa, many new, scientifically useful, and inexpensive space missions would become practical and affordable. In addition to garnering new knowledge, such missions would also provide more frequent opportunities for young scientists, engineers, and orbital dynamicists to gain hands-on experience in designing and executing deep space missions–experience that would be of great help to them when the time comes to tackle the more ambitious outer solar system and observatory missions that NASA hopes to fly in the coming decades.

——-

References

1. Pioneer Venus Project Information, National Space Science Data Center website: http://nssdc.gsfc.nasa.gov/planetary/pioneer_venus.html

2. Pioneer 6, 7, 8, and 9, Wikipedia article: https://en.wikipedia.org/wiki/Pioneer_6,_7,_8,_and_9

3. Stable Orbit for a Newly Discovered Companion, Centauri Dreams article: https://centauri-dreams.org/?p=17484

4. Horseshoe orbit, Wikipedia article: https://en.wikipedia.org/wiki/Horseshoe_orbit

5. Quasi-satellite, Wikipedia article: https://en.wikipedia.org/wiki/Quasi-satellite

6. TRW Space Log, Winter 1969-70, Vol. 9, No. 4, Pioneer E, TETR C entry on pages 40 – 43.
The National Space Science Data Center http://nssdc.gsfc.nasa.gov/ has a Pioneer E mission page at http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=PIONE.

7. Edward Belbruno, Wikipedia article: https://en.wikipedia.org/wiki/Edward_Belbruno

8. Edward Belbruno : Mathematics, Astrophysics, Aerospace Engineering (Edward Belbruno’s Official Website): www.edbelbruno.com

9. SpaceRoutes.com website: http://www.spaceroutes.com/intro.html

10. Hiten (Muses-A) JAXA webpage: http://www.isas.jaxa.jp/e/enterp/missions/hiten.shtml

11. Hiten, Wikipedia article: https://en.wikipedia.org/wiki/Hiten

12. Sentinel Space Telescope, Wikipedia article: https://en.wikipedia.org/wiki/Sentinel_Space_Telescope

13. Sentinel Mission website (mission overview page): http://sentinelmission.org/sentinel-mission/overview/

14. LTV (Vought) SLV-1 Scout, Designation Systems article: http://www.designation-systems.net/dusrm/app3/lv-1.html

15. Ford RM-89 Blue Scout I, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-89.html

16. Ford RM-90 Blue Scout II, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-90.html

17. Ford RM-91 Blue Scout Junior, Designation Systems article: http://www.designation-systems.net/dusrm/app1/rm-91.html

18. Blue Scout Jr, Encyclopedia Astronautica article (with launch chronology): http://www.astronautix.com/lvs/bluoutjr.htm

19. The Making of a Moon: The Story of the Earth Satellite Program by Arthur C. Clarke, pages 149 – 150 (First Edition, Published 1957 by Harper & Brothers Publishers, New York, NY, Library of Congress catalog card number: 57-8187 [a post-Sputnik revised edition, the same book with that update, was published in 1958])

20. Aeronutronics Farside, Designation Systems article: http://www.designation-systems.net/dusrm/app4/farside.html

21. Possible Challenge to Sputnik on Unmanned Spaceflight website: http://www.unmannedspaceflight.com/lofiversion/index.php/t1955.html

22. The First Shots Into Interplanetary Space by Professor Fritz Zwicky, California Institute of Technology Library website: http://calteches.library.caltech.edu/181/1/zwicky.pdf

23. Boeing to Design DARPA Airborne Satellite Launch Vehicle, Boeing.com website: http://www.boeing.com/features/2014/03/bds-darpa-contract-03-27-14.page

24. DARPA’s ALASA space launch system from airplane, wordlessTech.com website: http://wordlesstech.com/darpas-alasa-space-launch-system-from-airplane/

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Woven Light: The Orphan Obscura

by | Oct 2, 2015 | Culture and Society | 4 comments

Heath Rezabek began exploring Vessel, an evolving strategy for preserving Earth’s cultures and biology, in these pages back in 2013. A librarian and writer in Austin TX, Heath went on to push these ideas into the realm of science fiction, in the form of a series of excerpts from a longer work that is still emerging. The concluding post in this sequence appears below, though you’ll be hearing more about ‘Woven Light.’ A novel is emerging from this haunting look at how, at various points in our future and with a wide range of technologies, we will interact with the artifacts and stored experience of our past. Heath’s helpful synopsis begins the post.

by Heath Rezabek

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For some time, I have had in hand the final chapter – for now – of the Woven Light speculative fiction series as published on Centauri Dreams from 2013 to present. At Paul’s invitation, I am prefacing the final installment with some notes on the series as a whole.

The series began as a way to explore ideas surrounding the prospects for human or posthuman space travel, and the role which might be played by very long term archives in the resilience of life’s efforts to endure. I am not finished with the themes explored in the series, but for now it is time to shelve this particular approach to the storyline, along with its characters.

After feedback last year at the Turkey City Writer’s Workshop in Austin Texas, and encouragement from a few other parties, I am pursuing a new approach to the story arc, from an entirely different time and place in its imaginary history. The goal is to produce a cohesive and more linear novel, exploring world(s) we’ve only glimpsed so far; the Centauri Dreams installments of Woven Light are a (somewhat fragmented and dreamlike) hint at what is to come.

Here follow episode summaries of each of the published episodes, with links to their versions here.

Vessel Haven (I). We are introduced to an entity called Tracer Aakanthia [9T33], who is exploring a holographic archival site. We meet Aben Ramer, encountering a mock-up of a Vessel Haven – a very long term archive – at the Burning Man festival, circa 2023.

Adamantine (II). ?We meet Mentor Kaasura, who is exploring a ruinous region, the site of an ancient disaster. He rests at a pilgrimage shelter. We learn about an artificial life project meant to provide a guiding sentience for a starship. The sentience is named Avatamsaka; the starship – a lightsail – is named Saudade. We also learn about two offshoots of humanity: the Avaai and the Ghemaai.

Augmented Dreamstate (III). ?We meet Aben’s mother, Thea, an author of speculative fiction, as she struggles with a draft of her work. We meet Dr. Jota Kaasura, who bears an unknown relation to Mentor Kaasura from the prior installment. Dr. Kaasura is working on a project called Augmented Dreamstate, which allows the immersive visualization, exploration, and recording of scenarios. He explores one such: the scene on the day of a disaster.

Proteaa (IV). ?We explore a spaceborne habitat derived from an idea of Freeman Dyson, which he’d referred to as an Ark Egg. Here they are called Precursorae, and within them dwell beings called Proteaa. Vannevar Bush’s Memex is considered, along with an exercise developed by Thea Ramer for coaxing concepts out of a flux of random ideas: Wildcards. Dr. Kaasura meets someone unexpected, and dreams of drifting habitats far from the Precursorae.

Lesson Arcs (V). ?Thea Ramer publishes her novel, The Tracer Guild, but life has other plans. Years later, Aben Ramer meets Dr. Kaasura, and lays the groundwork for him to meet with Thea. In another time and place, perhaps aboard our lightsails, we meet Vaarea Ramer, one of the Ghemaai, immersed in worldbuilding lessons that are passed from mind to mind.

Age of Release (VI). ?Mentor Kaasura explores deep passages woven of light, beyond the shelter’s door. Far flung from there, a fog of mind called Ancient Light sifts the space between stars, finding worlds where planetbound life had nearly reached the Age of Release. Aben Ramer determines researches in one of his favorite spots for thinking, and makes a new friend.

For those who would like a plain manuscript version, in sequential order, this PDF can be found here. It includes a short Appendix of previously unreleased developmental fragments from the drafting table].

I look forward to sharing future excerpts from the new effort with Centauri Dreams as well, should Paul welcome it.

Here, at last, is the final installment (for now!) of Woven Light: A special series for Centauri Dreams, 2013-2015.

Woven Light: The Orphan Obscura (VII)

Across town, mother wasn’t doing so well.

Sorting had led to spreads, as Thea rediscovered cards she’d scribbled on years ago, and laid them out the way she remembered, five across to find three akin. She’d pull them aside, and then would remember. How it had felt: To write with an explorer’s eyes, cresting a hill to shine the light of awareness on inevitable mountains.

Eyes closed, still she could see Ityl-Atys spread below her. Wings outspread, a raptor keen and bright of eye . . . She could see the bazaar, the outlying districts, the towers of abandon. Red streaks in distant sun spread golden rivulets, a quilt of sands for all below them.

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Image 1: Based on photograph CC BY Michal Huniewicz.

And below, she remembered, delved Vaachez, his dusted hat long since traded in fair exchange for a rough and partial map; his map now guidance through at least one dimension of battered space.

Thea read an untold chapter to herself. So easily, but traceless. No recorder. This time, no traces. She only wanted to know.

~ I only want to know. ~

Vaachez made his way along the higher moraine, beams and slabs settled well for this stratum, clearstone lending its glow to light his way.

His pack was both lighter and more burdensome now, its baubles and bits traded for rarified things needed further down, when stealth failed him. So far, trading had sufficed. But trading had grown more scarce since the post where Oaami, his guide, had bowed, and remained behind. “All I have left to offer, I have whispered to this map,” she had said; and handing it to him, she had turned to her ascent.

From there, he had endured the broken way with only scrapes and the parching isolation of stealth to test him.

In time, even the need for stealth had faded, as the last small settlements carven into these caverns had scattered, and subsided altogether. But the weight he carried now was of most use down here; his ascent would depend on encountering someone else descending, the only ones for whom such things would hold the value they held for him now.

He’d had no word of other tracers when he’d ducked into the shade of the lower bazaar. He couldn’t depend on them. So far as he knew, he was the only pathfinder still drawn to this old mystery.

He had to know. Ascent or an ending, he only wanted to know.

Vaachez worked his way slowly around the edge of a drop, a good ten stories, rusty cable scraping the leather of his gloves, smell of dust and sunbeams still (thank the moon) refined by his breather.

Around the bend; only a little further, if this map was anything at all.

Across the way, just then, he glimpsed it: a bird of some sort, winged its way across the chamber above this blockage. Setting sunlight from a shaft far above them caught its wingtips: a dash of burnished wings. A piercing cry. Alight and keen, now, on the opposite ledge.

A clambering clatter in the softlight, ancient ledgers falling still. Vaachez stood, staring straight at the watcher and pierced right through in return. He couldn’t make out the size of the bird, but its shape was nearly regal. So sharp and feral, whittled by chance and opportunity.

It shifted one leg; he did the same. Nothing gave. Exhaling, Vaachez turned to see the rumored landing not a dozen streetwidths on. From there, by map, the ruins descended in wide slabs and steps, far enough that by the time he reached the fabled site, dusk would have fallen far above. Already the air was quickly cooling.

Inhaling again: ~ All things struggle ~. Exhaling again: ~ On each other we depend. ~ Vaachez switched his grip upon the cable, and stepped ahead.

From its perch, the great raptor could see the dustling balance and edge onwards, surefooted and determined.

Hours later, now sharpened in the cool air from his slow descent of switchbacks, he rested. Vaachez stood again on solid slabwork, trying to adjust his eyes to blue shadows. On beams and slabs around him, he thought at one point he had glimpsed vegetation. How possible was that, so far down below? He climbed the final rise, a silent beachhead, and stood before . . .

At first he saw a mountain. Before his mind could calm his heart he felt it sink at the thought of another climb. But no: this was an illusion. Peak there was, quite clearly rising, all in dusky blue and — yes — clad in clambering green. Darkling down below, it rose and reared at the peak as a beam full of moonlight was filtered down to impossible pools at the base of the beamwork.

And beamwork it was: a steeple of sorts, tentpoled and rising, rooted in its subterranean oasis, foundations wide at the base. There, perhaps, it sat: the Orphan, Obscura. How could he know?

Seeing himself at a ledge, an impassable drop to the oasis below, he stopped, and sat, and stared.

By now his eyes had adjusted quite well to the indigo dark, and he could see and sense that the ruin was extensive, though not as massive as some above ground. But sheltered in this space, this domed duskland, it seemed as if a miniature of something vast. Truth enough was that he couldn’t tell. It couldn’t be as large as it seemed. The space was so quiet, the air so still, the sound of water trickling so clear in the silence it carved.

Inhaling again; exhaling again.

Behind him, a cry: and a winged shadow passed not so far above his shoulder, on his right. Friend from the ledge-crossing, it needed a name. And as it made its way across the gap to perch on rising angles, he decided its name was Zinn.

The distance was greater than he’d thought; the edifice was huge. It slumber was deep. Its voice . . .

He sat before the Orphan. He would speak with it, or nothing.

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Image 2: Based on photograph CC BY-SA Al Jazeera

Letting his focus go soft, he steadied his gaze and his breathing, until before him in the settled shape of the ruins he could see a seated figure, Grandfather Silence, casting long shadows. And as his gaze drifted, it fell like the dust, and settled on wellsprings deep at the base . . . And tilted his gaze as he found there a gap of a threshold. Uncertain, he still saw what seemed like — another. Seated at the entry, a tiny mountain settled down beneath the mountainous shadow. Who would break the stillness? Who would answer?

He broke the stillness. ~ I sit before you, a traveller and a friend. I have heard only whispers, but even rumors have a cause. ~

Only dust in deep night air, so slowly.

~ I am called Vaachez. I am an orphan like you. ~

And as Zinn watched, the figure sat with silence.

And the silence stretched on, and on.

~ He has come a long way, ~ croaked Zinn. ~ He has come to know your tale. ~

The Orphan Obscura stirred then, and murmured; ~ He knows it already. ~

Zinn shook and settled, a flutter and a silence like an avian shrug. ~ He may have forgotten. ~

~ Then he is not the one to discover it anew. ~

Zinn cocked one eye, and sized the dustling up and down. ~ He may be the last. Their house is fading. ~

~ He may be the first. Their house is a seedling. ~ The Orphan Obscura shifted something, from one place inside its expanse to another.

~ If he leaves without knowing, he leaves without purpose. ~

Obscura muttered. ~ If he leaves without knowing, he leaves too soon. ~

Perturbed by this back and forth, Zinn took wing, sailing up into the rafters, and swinging down towards the base, where Vaachez’ watery eyes were still fixed. And landing there, she found a pile.

~ What is this heap? ~ She picked at the leaves.

~ It sits and waits. ~ Obscura surveyed a shallow pool at its feet, located a treasure.

~ No time to wait! ~ A fluttering dance. ~ The sun is near! The moon is full! The sleepy stir and soon they’ll wake; for what, a pile? A heap of memories? ~ Zinn darted down to peck at something shiny.

~ A heap of time, slow and intact. That is no small thing. ~ Obscura turned a stone slowly in its gaze, and beneath the stars its etchings caught the ancient light. ~ I have done what I can. ~

Zinn circled the stack of remnants there, wondering if Vaachez could read at such a distance.

She decided he could, and took wing.

~ You’ve done what you can; and so have I. ~

Vaachez sat, parched and quite lonely. The bird had flown suddenly, surely, up and beyond the loose strata far above him. He was alone with his vigil.

Before him slumped a place where forgotten things slept, and waited for a stronger will than his to wake them. But Zinn had been right about one thing: his eyes were keen. And he could read, in that cairn of debris far below, a secret hint of kindness.
Vaachez mulled his reckonings.

All about him, far above him, intolerable weight bent, balanced over its remnants. The Orphan Obscura was not alone, and several more of its kind lay at rest, he knew, slumbering guardians at the roots of other citistates. But if they were all as drowsy as Obscura, there was no way the long work of the Tracer-Guild, and the pathfinders before them, and the dreamhunters before that, could ever come to fruition.

~ Sojourner, peace. You are not alone; nor am I. ~

Vaachez opened his eyes, not realizing they’d been closed, to see the color changed in this space from dusk to slow dawning. He leaned in, peering closely at the form at ruin’s threshold, before the climbing light in this chamber swamped his eyes. Already it was growing violet.

~ A thousand ruins does not a remembrance make. ~ Vaachez furrowed, scolded the fading night.

~ A thousand and one. It takes only one, unruined and found, to spark a rekindling.
~ Obscura raised its gaze, and still could see the moon. Something on its surface glinted, and it too was unalone.

Vaachez rose. Of course the citistate Orphans weren’t the only Orphans out there. Just the most encumbered.

He would find another. He would find a site intact. Would he have to leave the Tracer-Guild, or would they understand?

He looked down at the water, hoping it wasn’t a trick of the mind. He’d need to fill his skins before he made his ascent. Shifting his glance to his rope, he surveyed the situation. He had to get down there, and he had to get back up.

Now that he knew what the seated one sat with, he believed he could see a way. Weighing his chance in his hands, he took it.

The cavern was filled with sudden sun.

– – –

Thea awoke, late afternoon blazing low on mountaintops.

“Shit. You’re kidding me.”

Why no recorder? She was out of practice, and should have known she’d fall asleep. She turned to sit, fumbling for her pad. What was it? A greenish-blue tent in a forest; winter trees overhead; a nightingale?

“Stop and go back.” She clenched her eyes shut and hit record.

“There was a tent, and a full moon. Someone sat and watched and waited. A birdsong, down at the base of the tent… A pile of leaves? A pile of papers? Stones? A pile of something.”

Shit…

“But there was a glimmer in there, underneath or beside it… And I got the impression there are others. Other campsites I guess . . .”

Thea picked at a quilt thread.

“. . . In greener forests . . .”

Greener than green. “All those years, I was afraid of ending this thing.” She looked over at her bedside shelves, at her work, paperbacked.

“Work. I’ve got work to do. At least I should finish the report. Where’s Aben?” She went to send a message, then remembered her son was a grown man already.
Bluer than blue. “I lost it. I’ll try again tomorrow. This time I’ll record from the start. It’s never the same, but it should be related.”

She shut it off, and went to splash her face, and sat at the kitchen table to read back what she had so far.

~ So reluctant. ~

Thea Ramer looked at her life and she sighed.

~ Just sit with it. ~

The sunset lit the pictureframes, the plants and books, the shiny coat of little Dakini, the calico kitten up on her shelves. Golder than gold.

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Image 3: Based on photograph CC BY-SA Ryan Cadby

– – –

Notes on the Deployment of Survey Swarm 2B “Peripheral Vision”?(New York City, Friday September 1, 2023)

The second phase of our survey project utilized a reoptimized scanning algorithm which sought to double the scale and resolution of the initial test survey. My lab at Cornell had developed the algorithm based on analysis of the 2022 data which had suggested that the storage format could accommodate far greater density than we were requiring.

Project lead for the algorithm now known as Peripheral Vision was Ph.D. Candidate Kim Tran, under my supervision. I take full responsibility for what ultimately ensued.

Once site preparations had been completed, the fleet of 64 surveyors were arranged in their starting hexagonal configuration, facing inwards towards the calibration artifact, precisely as specified. The target artifact was a solid tungsten sphere, measuring 20cm in diameter.

The process as planned was for the swarm to self-arrange into a dome configuration around the calibration artifact, and then to commence scanning at n=1 resolution.

Once that scan had been completed, each surveyor was then to pair randomly with another of its peers, the two swapping position to rescan at the same resolution from the new position as an error check and redundant sample.

Finally, once all 32 pairs had completed this process, each would re-select a different random partner, swap positions, and reset their scanning matrices to twice the resolution of the prior pass.

They were then to widen their distance from each other — and thus the swarm’s distance from the artifact — by twice their prior distance, and the process was then to be repeated. The scanning was to cease after four iterations, with a failsafe killswitch coded to kick in after that point if anything in the process had impeded the scan.

– – –

Thea stared through her words, sunken in recollection of what had happened that day.

It could have been much worse. They had lost the swarm, and several technicians had been sent to the ER with concussive shock from the blast. Really, the blast could have been much worse. It all could have been much, much worse.

And then there was the dataset. She turned from her words to stare instead through the dataset.

Aleph. The Myriad Arcana.

When initiated, it had seemed as if the swarm had failed from the start. They failed to reposition at greater distance after the first scan, or the next. Focal beams of bluelight saturated the chamber, tracing and retracing the sample sphere. One sweep; two sweeps; four; then more. Still they hovered, frantically scanning the sphere.

Because sampling had continued to double, even though the surveyors were not repositioning at all, the failsafe code was not engaged. Or perhaps that code knew something its technicians didn’t: it was only when the manual killswitch had been kicked that the surveyors blew to shrapnel, taking out half the observation deck’s retaining wall.

Thea and her team had driven the evacuation, and so she could see light of day beyond the lockdown door when the swarm blew. Flat she laid on pavement, primal fear rekindled to a flaring all around her.

But because the doubling data had shed itself instantly abroad, syncing and resyncing in distributed backups as planned, they still had the bulk of its tattered core. For better or worse it had been unquarantined, because of course they’d immediately want to vouchsafe the data as it streamed from the site… No-one had asked about this yet in the investigation; still it kept her sleepless.

The dataset was so dense that it had already been dubbed a data core by some of her students, and they had only just begun to sample its surface. It had swamped and choked their servers as it had formed, and then their distributed syncs and backups. But now it sat, inert and crystalline, arrayed as woven light; and it could be viewed. Visualized and contemplated, spinning like an ashen star in problem space.

Because it was so large, it had been a lucky break that the syncs had been distributed from the start, or they would never have been able to glimpse it as a whole at all. Yet now, each time they did, each time they sampled a slice and arrayed it with others, they found both gaps and gifts which shouldn’t have been there.

Elements too nearly related for their sampling process to be verified as random.

Samples whose content seemed nothing to do with tungsten.

Avatamsaka had been unborn.

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An Asteroid Deflection Investigation

by | Oct 1, 2015 | Asteroid and Comet Deflection | 16 comments

Yesterday’s post on what we’re learning about Rosetta’s comet (67P/Churyumov-Gerasimenko) briefly touched on the issue of changing the orbit of such bodies for use in resource extraction. Moving the comet Grigg-Skjellerup is part of the plot of Neal Stephenson’s novel Seveneves, where the idea is to support a growing human population in space with the comet’s huge reserves of water. Just how hard it would be to move a comet is made clear by how a proposed near-term mission approaches the question of deflecting a small asteroid.

The mission, discussed at the ongoing European Planetary Science Congress in Nantes, is called AIDA, for Asteroid Impact and Deflection Assessment. A joint mission being developed by the European Space Agency and NASA, AIDA is actually a two-pronged affair. ESA is leading the Asteroid Impact Mission (AIM), while NASA is behind the Double Asteroid Redirection Test (DART). The plan is to rendezvous with the asteroid (65803) Didymos and its tiny satellite (known informally as ‘Didymoon’) for scientific study and a deflection test.

Think about this comparison: Comet Grigg-Skjellerup (studied by the Giotto probe in 1992, though from a considerable distance) is approximately 2.6 kilometers in diameter. Didymos is about 750 meters in diameter, and the Didymoon about 160 meters across. It’s the Didymoon that ESA and NASA plan on deflecting, driving the DART spacecraft into it as AIM observes and analyzes the plume of ejected material. With AIM remaining on the job, further mapping and monitoring will study the impact area and reveal any changes in Didymoon’s orbit.

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Image: Arrival of AIM at Didymos and Didymoon. Credit: ESA.

Thus the spread between a near-future science fiction story (the acquisition of Grigg-Skjellerup for resources in Seveneves) and present-day technology — we can assume that Stephenson’s comet-catcher has some powerful propulsive assets compared to what we can deploy today. But the novel explains all this on its own terms and I’ll say no more about it. As to AIDA, the words of Patrick Michel give us the gist. Michel is lead on the AIM Investigation team:

“To protect Earth from potentially hazardous impacts, we need to understand asteroids much better – what they are made of, their structure, origins and how they respond to collisions. AIDA will be the first mission to study an asteroid binary system, as well as the first to test whether we can deflect an asteroid through an impact with a spacecraft. The European part of the mission, AIM, will study the structure of Didymoon and the orbit and rotation of the binary system, providing clues to its origin and evolution. Asteroids represent different stages in the rocky road to planetary formation, so offer fascinating snapshots into the Solar System’s history.”

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Image: Impact on Didymoon, as observed by AIM and its deployed CubeSats. Credit: ESA.

AIM would launch in October of 2020, with rendezvous at (65803) Didymos in May of 2022. Didymos rotates rapidly, about once every 2.26 hours, and is considered the most accessible asteroid of its size from Earth. Didymoon orbits Didymos every 11.9 hours at an altitude of 1.1 kilometers — the name Didymos (Greek for ‘twin’) was chosen by astronomer Joe Montani, who discovered the objects, when light-curve analysis revealed the binary nature of the asteroid. While Didymos is thought to be a ‘chondrite’ (stony) asteroid, we know nothing about the mass and density of Didymoon, a lack that AIM and DART would be able to correct in short order.

The AIM mission has echoes of Rosetta, for like the latter, it carries a lander. MASCOT-2, built by the German aeronautics and space research center (DLR) will probe the internal structure of Didymoon, emitting low-frequency radar waves that will pass through the object, allowing AIM to chart the deep structure of the asteroid even as it measures Didymoon’s density and maps the surface at visible and infrared wavelengths. DART’s impact with Didymoon is scheduled for October of 2022. I also notice that AIM is scheduled to deploy three CubeSats to assist with impact observations and to test communication links between satellites in deep space.

DART itself is a 300 kg impactor that is designed to carry no scientific payload other than a 20-cm aperture CCD camera to support guidance during the impact approach phase. Launch is currently proposed for July of 2021. The impact at 6.25 kilometers per second is expected to produce a velocity change in the range of 0.4 mm/s, which should change the relative orbit of Didymos and Didymoon but create only a slight change in the binary’s heliocentric orbit.

Related: NASA has funded a concept design study and analysis for a mission called Psyche, which would investigate the interesting asteroid of the same name. Psyche is thought to be the survivor of a collision with another object that stripped off the outer layers of a protoplanet. About 200 kilometers in diameter, it is thought to be the most massive M-type asteroid, with a surface that is 90 percent iron. The Psyche mission, led by Linda Elkins-Tanton (Arizona State) would be an orbiter that would launch in 2020 and arrive in 2026.

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