“Space is caffeine for learning.” A.C. Clarke
Space Horizons 2017 — Destination: Alpha Centauri was held February 15th and 16th at Brown University in Providence, Rhode Island. The annual Space Horizons conference covers almost-ready-for-flight space topics. The subject was centered around sending swarms of tiny, postage-stamp sized spacecraft to our nearest neighboring star systems.
This report includes a general proposed architecture, the workshop schedule, some take-away observations and my initial design research output from the lunchtime poster session.
As always, Professor Rick Fleeter (Brown/La Sapienza) organized the workshop, this year with student lead Kat Pisani. The format varies some years, but this year it followed the pattern of a Wednesday early-arrivals talks followed by an intense, all-day workshop on Thursday consisting of panel discussions, talks by professionals and . The official website is https://spacehorizons2017.wordpress.com/
General Proposed Architecture
Destination: Alpha Centauri examined proposals, research and funding to develop and fly swarms of postage-stamp sized spacecraft called WaferSats or ChipSats at relativistic speeds (0.3c is commonly cited) to the Alpha or Proxima Centauri (Rigel Kentauri) star systems. Rigel Kentauri is the current most-interesting target due being the closest star to our own Sun and confirmed to have planets.
Generally, a large phased-array laser Directed Energy (DE) cluster in the 100-300MW power range would be installed on the lunar Farside in such a way that it can’t ever face Earth or our geosynchronous satellites. The propulsion laser is automatically going to be perceived as a “weapon” so it needs to be emplaced cautiously for policy purposes. The laser array boosts each individual WaferSat to 30% light speed (.3c) in ten minutes and can propel about 40,000 chips per year in a continuous stream that extends between the stars. The result, in theory, is a massive, low resolution, interferometer stretching across several lightyears that contains the needed sensors to image planets and moons in the star system(s) they pass through. At .3c the WaferSats require about 20 years transit time to fly by the closest target stars.
Additional uses for the laser propulsion system include power transfer to other spacecraft as part of a space-based beamed-power network and for boosting much heavier payloads like crewed capsules. A 1-gram WaferSat can achieve .3c, a 10-ton capsule can be accelerated to get to Mars in a few weeks instead of six months, using the same system. Professor Fleeter describes this as, “The opposite of missions is infrastructure.” The technology advances could include in fiber laser amplifiers for photonics applications and system-on-a-chip devices for everything from aerospace to medicine to environmental monitoring. “There’s a lot to be done along the way and the more it has other uses the better.” according to Jordin Kare.
The teams working on various aspects of this include The Breakthrough Foundation, Dr. Lubin’s Experimental Cosmology Group at UCSB, Dr. Cahoy from MIT’s StarLab and LaserMotive, among others. Breakthrough has a budget of $100,000,000 dollars in overall funding between Starshot, Listen and their other space projects. This massive injection of private capital is important as it circumvents any protesting over government funding plus they award prizes to researchers doing useful work. UCSB’s Phil Lubin is developing WaferSat spacecraft and the phased-array lasers to drive them. Dr. Cahoy models communication systems at light-year distances and poses questions such as “How many photons do you need to form a bit?”. Jordin Kare of LaserMotive is turning his work on space elevators and laser-powered quadcopter drones toward the practical aspects of launching these relativistic WaferSats.
Other proposed technology paths and questions include using a diamond-wafer particle accelerator or other particle beam instead of lasers, using larger CubeSat-scale craft and whether each chip should communicate with Earth directly or intercommunicate in the swarm first.
- Wednesday February 15
- Michael Walthemathe, Ruhr-Universität Bochum, on importance of extending human reach beyond the solar system
- Phil Lubin, UC Santa Barbara, on progress toward realizing interstellar missions
- Thursday, February 16
- Larry Larson: Welcome
- Rick Fleeter : Introduction to Space Horizons
- Pete Klupar: 2017 Keynote Address
- Jim Head: The Science Imperative
- Philip Lubin: ChipSat and laser propulsion
- Ruslan Belikov (NASA Ames), Gregory Tucker (Brown University), Pete Klupar (Breakthrough Foundation) and Emily Gilbert (University of Chicago) on: The value of going to Alpha Centauri plus remote observation from near Earth
- Panel: Going There vs. Observing From Here
- Lunch and student posters
- Kerri Cahoy: Communication link from a low power chipsat 4+ light years away
- Zachary Manchester: Flying ChipSats
- Jordin Kare: Separating Power Source and Vehicle
- Michael Walthemathe: engaging society in exploration
- Panel: Societal impact of interstellar exploration
“Low reliability ideas, high reliability hardware.” – Rick Fleeter
Professor Fleeter pointed out that there are thousands of ideas about what to do in space but only a few of which ever actually fly. This appears to scale with the extreme reliability of space hardware.
The main point of the workshop was that we could do this right now but some components are to expensive for it to be practical. A few more years and some developments in manipulating laser light and it will be affordable. This could create the next leg of a transportation network for developing our solar system while exploring neighbors like Rigel Kentauri. Such a DE array could help build massive space telescopes and provide a range of technical advances to any industry that uses lasers. The people developing the first trip to the stars are clearly focused on the technical and economic journey and it’s inspirational potential more than a single end goal. The amount of time, money and careers going into this project require long-term thinking.
Some combination of ChipSat swarms and phased-array laser clusters are probably the best way to fly. Separating thrust from craft is probably essential as Dr. Lubin had a presentation that showed how getting matter to relativistic velocities requires propulsion with relativistic exhaust velocities. This mostly excludes putative fusion drives and leaves only antimatter and Directed Energy as propulsion source candidates.
Much of the focus is on commercial-off-the-shelf hardware (COTS). For example, Dr. Lubin’s test arrays use standard DSLR camera lenses hooked up to fiber optic lasers. One issue made clear by all the researchers involved is that fiber laser amplifiers need to become much cheaper for Destination: Alpha Centauri to make economic sense. A goal of $1 or less per watt seems achievable, Dr. Cahoy pointed out that the fiber amplifier in a DVD drive costs about ¢.10 for the 1-watt element. Mass-produced, space-rated fiber amps should be able to be priced within an order of magnitude if enough are being made.
At Space Horizons 2016, Dr. Phil Metzger presented an idea of a boot-strap outer space industrial economy of self-replicating machines. At first, they just make low-efficiency solar panels or other simple objects. Over the course of several decades, the machines create an exponentially increasing industrial base. This topic came up separately this year as a way to enable interstellar flights through automated manufacturing and assembly.
Directed Energy boost creates in-system superhighways for nearby payloads to Mars and other destinations. DE may turn out to be a preferred means of propulsion, electricity and process heat for future inner solar system development, especially of Mars and Lunar craters.
A potential research point I’d like to see addressed before hardware is completely specified is whether microwaves, specifically in the 2.45 and 5.8 GHz ranges, can achieve similar results to a laser array. This would be specifically for integration in a putative Space-based Solar Power (SBSP) demonstration network.
Wafersats might be able to be propelled by a demonstration-level Solar Power Satellite (SPS) in Earth Orbit. This would involve a 100-300 kW beam-forming microwave antenna, likely in polar orbit and powered by solar panels. An assessment should look at recent advances in phased-array microwave sandwiches and life cycle assessment of both systems as part of an integrated beamed-power system. The analysis would look at the trades between lasers as an end output of a power system whereas the SPS would be part of the power system. There should be an effort to include power-beaming in some form in whatever external propulsion system is developed. One immediate issue is beam-focus and whether active beam-forming could address some of the concerns without also flying relativistic mirrors as proposed by Dr. Forward in Vulpetti, Matloff and Johnson (2008). Proposed microwave “sails” have footprints that are orders of magnitude larger than proposed light sails.
Development of the Wafersat system could potentially benefit from this sort of integration with a beamed power network beyond supplying a Farside laser array with electricity. The SPS satellites could potentially serve as a DE propulsion system that can’t work as a weapon.
Design Research Exercise: Technical & Social Imaginaries of Destination: Alpha Centauri
Instead of a poster, I ran a simple design research exercise during the lunchtime poster session. The exercise consisted of a SWOT Matrix and an I Like/I Wish/What If list. SWOT stands for Strengths, Weaknesses, Opportunities and Threats; it is a very fast and efficient method for dissecting an idea, situation or scenario. I Like/I Wish/What If is a technique utilized by Stanford’s D.School for team ideation. Participants filled out each section, then ranked all the entries with dot stickers to indicate what they thought were most important in each category.
The most important Strengths of the concept were the vision and inspiration it can provide for children, the infrastructure aspect of multi-use directed energy arrays and having that kind of high-energy laser technology for other applications.
The greatest Weaknesses cited include the very large upfront costs and the possibility of the laser location not being under US control, which was also cited as an opportunity.
Opportunities behind Destination: Alpha Centauri include routine, fast access to our own Solar System (again, infrastructure that plays many roles) especially “student ChipSats of infinite types”, technical spin-offs, public engagement and interstellar dating. Several allusions to social networking with aliens were made across the exercise but ranked low. Everyone involved seems to hope the project will help us find life or even intelligent, technical species but aren’t holding those hopes to high. The last opportunity that was ranked by another participant was the so-called Overview Effect, the change that people experience in seeing the world from space.
Threats cited include the perception of these tools as weapons and their potential to spark a space arms race and the loss of interest should the first project fail.
Participants Liked that the laser arrays would likely be a multi-use, multi-party piece of infrastructure. One entry suggested piles of large, unmarked bills.
Participants Wished that there was a near-term and smaller scale space-based test “to start playing with photon delta-V”. This is in some ways an obvious stepping stone between laboratory benchtops and megawatt facilities on the Lunar Farside but is also the exact kind of policy nightmare regarding space-based weapons that no government would allow to fly, private mission or public. One unranked idea that was discussed elsewhere in the workshop was “brakes” of some kind at the destination star. As it is, the individual WaferSats pass through the target star system in a few hours traveling at relativistic speeds. The advantage to Dr. Lubin’s proposal is that thousands of these craft make that journey in a continuous mesh.
What If questions included “What if I could change the gravity constant” and whether there are aliens and how that would impact the project and our understanding of our place in the universe.
These process photos include the final results, two development pictures and one of researchers participating in the exercise. In my experience, space scientists and engineers are often surprised and excited when designers bring our research tools to help them analyze their chosen fields and projects.
Space Horizons is always an interesting conference. Professor Fleeter knows all the interesting people in the space sector and brings a keen sense of understanding what is nearly possible and about to happen in space projects. This year’s topic was closing a circle as the first Space Horizons was about ChipSats when they were a completely new concept. Now the discussion isn’t whether ChipSats or Wafersats for Dr. Lubin’s team are possible but whether they are appropriate as our first interstellar emissaries.
Real action is happening on this right now at deepspace.UCSB.edu, Breakthrough Foundation, Lasermotive and other labs across the US. This concept, whether as StarShot or another team, presents enormous commercial and academic opportunities along with workforce development, youth inspiration and the potential of a new “Earthrise” moment from 4 lightyears distant.
- Vulpetti, G., Johnson, L., & Matloff., G. L. (2008;2009;). Solar sails: A novel approach to interplanetary travel. New York, NY: Springer-Verlag. doi:10.1007/978-0-387-68500-7