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2017 from an Interstellar Perspective

The recent burst of interest in interstellar flight has surely been enhanced by the exoplanet discoveries that have become almost daily news. Finding interesting planets, some of them with the potential for water on their surfaces, inevitably raises the question of how we might find a way to get there. We can only imagine this accelerating as missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope begin to fill in not just our inventory of nearby planets but our understanding of their compositions.

Find a terrestrial class planet around another star — we may find that there is more than one around the Alpha Centauri stars — and the interstellar probe again becomes a topic of lively conversation. Breakthrough Starshot, the hugely ambitious attempt to develop a concept for tiny payloads being delivered through beamed laser propulsion to a nearby star, is by now a major part of the discussion. And as I said in my closing remarks at the recent Tennessee Valley Interstellar Workshop in Huntsville, there is a synergy among these developments.

Here’s a bit of what I said in Huntsville:

The emergence of Breakthrough Starshot clearly changes the game for everyone in the interstellar community. We have a congressional subcommittee report that ‘encourages NASA to study the feasibility and develop propulsion concepts that could enable an interstellar scientific probe with the capability of achieving a cruise velocity of 10 percent of the speed of light.’ I doubt seriously that that phrasing would have emerged without the powerful incentive of the funding provided by Breakthrough, nor would the Tau Zero Foundation’s recent grant.

Let’s take this apart and look at the pieces. We all know that Breakthrough Starshot lit up media coverage of the interstellar idea at the same time that we were finding an interesting planet not so much larger than Earth in what appeared to be a habitable zone orbit around Proxima Centauri — being at one of the Breakthrough Starshot sessions when the announcement was made was an energizing experience, and I remember staying up late one night in Palo Alto writing the article on the Proxima Centauri discovery that I would post when the embargo lifted.

Image credit: Manchu.

The subcommittee report I referred to was the work of representative John Culberson (R–TX), long known for his interest in the space program and a panelist at the TVIW 2017 gathering. Culberson submitted a report to the Committee on Appropriations to accompany a bill setting NASA’s budget for the 2017 fiscal year, which began on October 1 of that year.

The bill sets down a futuristic agenda:

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). 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.

Part of this study would be focused on Alpha Centauri, as the report makes clear:

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.

And there is this about propulsion prospects:

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. 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.

The report notes work at the NASA Innovative Advanced Concepts program, pointing to studies Phil Lubin (UC-Santa Barbara) has performed on the whole issue of beamed propulsion using lasers. This work is repeatedly cited by Breakthrough Starshot and Lubin is actively involved in Breakthrough’s work on laser technologies. Thus there is some overlap even here between NASA and a privately funded venture that is putting the beamed sail idea to the test and examining the infrastructure needed.

What Culberson’s report went on to do was to tell NASA to submit an “interstellar propulsion technology assessment report” with a draft roadmap that could include an overview of the propulsion concepts considered viable, one that would include the technical challenges, assessments of technology readiness levels, near-term goals and funding requirements.

If this sounds familiar, it is because of the tie-in with the grant recently awarded to the Tau Zero Foundation to compile just such a technology roadmap, work which is now in progress. But despite overstatements in many media outlets (along the lines of ‘NASA Planning Interstellar Mission’ and the like), funding breakthrough propulsion ideas is difficult at the best of times, as Tau Zero founder Marc Millis knows all too well. The former head of NASA’s Breakthrough Propulsion Physics project, Millis told me that acquiring the Tau Zero grant was an extended process that took a number of years to complete. From a recent email:

“A part of this story is the funding process. Those processes are not as singular or straight forward (or fast) as many envision. For example, the grant awarded to Tau Zero in January 2017 was proposed to NASA five years earlier, in February 2012. At that time NASA agreed that such work was needed, but was out of scope for its current funding categories. As those five years passed, the details of the work were iterated with NASA four times, each time getting closer to being funded. The last requested revision was December 2016, where Culberson’s interest added the last nudge. The other part of this story is that funding can vanish faster than it is awarded. In multi-year grants, like the one to Tau Zero, there is no guarantee that funding will exist for its second and third years. That is all part of the realities that we have to deal with.”

In other words, although I’ve seen the ‘NASA to the stars’ story pitched as a reprise of the Apollo program, it is actually a very small step in the direction of assessing what would be required to get an interstellar option in motion. This is certainly not a funded effort to build and launch specific hardware, or even a detailed mission study of the sort Breakthrough Starshot will be creating. But we do have recent reports that a small team based at the Jet Propulsion Laboratory is working on further ideas. JPL’s Anthony Freeman spoke of the possibilities at the 2017 American Geophysical Union conference. At the Huntsville TVIW meeting, JPL’s Stacy Weinstein-Weiss discussed the science prospects for an interstellar probe.

Obviously, we’ll follow such efforts with great interest. Meanwhile, my assumption on the background of all this is that Breakthrough Starshot’s sudden emergence prompted questions about NASA’s interest in interstellar matters on the part of Rep. Culberson, who off-loaded the idea to the committee report, which led to the awarding of the Tau Zero grant, perhaps intensifying the JPL investigations as well. A cynic might question whether the whole story hasn’t received far too much attention, given the excesses of many headline writers. But I have a different take.

In my view, keeping deep space in front of the public is helpful as long as we are pointing to legitimate research that moves the ball forward. The idea that NASA has a large interstellar program in place is incorrect, but that it takes even small steps in this direction by way of early conceptualizations and roadmaps is encouraging. Meanwhile, a vigorous private effort to put theoretical technologies to actual prototype and testing is all to the good, perhaps pointing toward future synergies between space agencies and non-traditional space organizations.

Everything gets blown out of proportion somewhere on the Internet, a challenge we all have to live with as we pursue ideas as futuristic as travel to other stars. But on balance, I’d say that 2017’s flurry of media attention was a good thing, and one that may remind us how much it would take to actually build serious interstellar hardware by 2069 or sooner. Technologies need development at every level, but there is nothing wrong with the Starshot model, beginning with conceptual studies and progressing to laboratory work that could point to eventual starflight.


{ 21 comments… add one }
  • Mark Zambelli January 6, 2018, 8:12

    That Culberson chap sounds like a wonderful proponent to have on the side of all those interested in deep space exploration. Let’s hope he doesn’t plan on going anywhere soon.

  • Andrew Palfreyman January 6, 2018, 9:34

    There is but a single idea for doing interstellar travel before 2069 in reasonable travel times, and that’s the Breakthrough Starshot concept. So why NASA is flirting with other possibilities utterly evades me.

    • ljk January 8, 2018, 12:33

      To at least appear relevant to stay in the space game? When you’ve got billionaire Elon Musk – and to a lesser extent Jeff Besos – practically operating their own space programs using NASA’s own launch pads and other resources, while another billionaire, the Russian Yuri Milner appearing to have cornered the interstellar exploration and SETI/METI sides of the space field (and maybe even Sol system exploration with his declaration to send a probe to search for life on Enceladus ahead of NASA), no doubt the venerable space agency wants and needs to do something to appear and stay with the changing times.

      Their 2069 interstellar effort may be little more than a few people doing a paper study at JPL, but they can count on the media to overhype it (and they sure did) and thus get the public thinking that NASA is going to Alpha Centauri real soon – probably even utilizing that secret Warp Drive project so many keep assuming the space agency is working on as well. This way NASA can get others to make it look like they are working on interstellar spacecraft and searching for aliens without actually having to do it themselves and get into trouble for overselling and outright lying.

      Sure, Trump told NASA to put humans back on the Moon, but there was no real plan or, most importantly, a serious budget increase to make this mandate happen. Meanwhile NASA has to suddenly switch gears from Mars to the Moon. It also doesn’t help that America has had to rely on Russia to get to the ISS since 2011 and that the Orion and SLS have been delayed for years while Musk makes it look like he’s launching rockets into space every other week – and landing them back on Earth!

      • ljk January 8, 2018, 13:10

        Oh yeah, and Musk is doing “cool” stuff like planning to send his own red sports car towards Mars – all with his own rockets and, most importantly, his own money:



        You can say it is just a publicity stunt, and it is, but it shows that Musk knows how to get the attention of the public in a very effective way. Now while NASA could not do something similar without the public and politicians literally screaming about them wasting their tax money, they really need to pay attention to this and find a way to boost their own projects. I mean, it’s space, for crying out loud!

        As with many other aspects of modern society, the space industry and its fans need to change our attitudes and perspectives to adjust to current mindsets. Otherwise NASA and other space science efforts will be seen as dinosaurs and treated as such – as museum pieces and sheer entertainment.

        FYI: NASA used to test launch their rockets such as the Saturn family by putting a lot of water as ballast in the final stage. It may have been politically safe but it won’t sell the program like a red sports car. To add: Some day space archaeologists and historians are going to appreciate finding a well-preserved automobile from the early 21st Century thanks to Musk.

  • Michael January 6, 2018, 15:11

    Starshot is not just about interstellar travels but about moonshot, asteriodshot, solarlensshot and planetshot….ect.

  • Jim Early January 6, 2018, 17:01

    In the late 1990’s under Goldin there was a small program called the “NASA Interstellar Initiative”. Were there any reports from that program that would be of interest to people trying to start a new interstellar studies program?

    • Paul Gilster January 6, 2018, 17:21

      This would be the effort that Les Johnson headed up at MSFC. Let me float that past Les in terms of papers specifically from that period. I’ll report back on what I find.

    • ljk January 8, 2018, 12:37

      I distinctly recall Goldin being genuinely surprised when talking to the public that they weren’t as excited about things like the ISS over sending humans to Mars and looking for alien life. Talk about out of touch with the people footing the bills.

      I also recall Goldin talking about an interstellar probe the size of a soda can being launched circa 2030 as a kind of bandaid to the above. Sadly it had about as much substance as NASA’s 2069 probe plans for Alpha Centauri.

    • ljk January 8, 2018, 12:51

      Do not forget the Innovative Interstellar Explorer (IIE):



  • Harry R Ray January 7, 2018, 14:48

    “Finding interesting planets…raises the question of how we might…get there.” Finding interesting exomoons would do the same thing. I am betting heavily on the prospect that the FIRST CONFIRMED exomoon will be announced THIS YEAR, albeit not necessarily the first potentially habitable one, and not necessarily from the most likely source, either. David Kipping just tweeted this 14 hours ago: Calling exoplanet collegues! Looking for previous literature which compares and interprets @NASA Kepler transit depths with those from @NASA Hubble WFC3. @StellarPlanet@jiffplanet@AstroCaroline@ExoSing. It looks to me like Hubble data on the October 29, 2017 transit of Kepler 1625b might not match up with what he expected.

  • ljk January 9, 2018, 14:58

    “To those devoid of imagination a blank place on a map is a useless waste; to others the most valuable part.” (Aldo Leopold, 1887-1948)

  • John C Mruzik January 11, 2018, 20:32

    So, but just a lurker, not a scientist. Just an MD. by if the Bussard Ram Jet even possible?

    • Paul Gilster January 11, 2018, 20:46

      John, have a look in the archives here, searching under ‘bussard.’ One of the big problems with the Bussard ramjet is, as shown by Robert Zubrin and Dana Andrews, it tends to create huge amounts of drag, which would make it perhaps more feasible in a magsail configuration for braking at a destination stellar system. Another problem: Lighting the reaction, which would require a substantial percentage of lightspeed just to get it going, and would also require a region of space with enough interstellar matter in it to make it possible. So while the idea is still out there, I think the early enthusiasm for it has been sharply tempered.

  • John C Mruzik January 11, 2018, 20:51

    Thanks! Disappointed.

    • ljk January 12, 2018, 11:49

      There are now more efficient interstellar probe concepts, even though the Bussard ramjet has the appearance of being elegant with its concept of scooping up fuel as it flies through the interstellar void.

      For one thing, it has been estimated that the Bussard scoop would have to be the size of a small world in order to collect enough interstellar hydrogen to make its fusion propulsion engines work. Either making a physical scoop or devising some kind of electromagnetic funnel to make this happen would be prohibitive.

      The Orion nuclear pulse vessel could still work, and we have the fuel and the technology to make it happen now, unlike just about every other plausible starship concept:


    • J. Jason Wentworth January 12, 2018, 14:22

      John, while this is far off, even if it will work, there is one highly-speculative ramjet possibility:

      As *this* “Centauri Dreams” article (see: https://www.centauri-dreams.org/?p=37828 ) inspired me, Brice Cassenti designed one of the few (if not the only) ramjet designs–using a toroidal ramscoop–whose drag would not exceed the starship’s thrust. The acceleration would be quite low, though–just 0.01 g or so–but if maintained long enough, relativistic velocities could be reached, and:

      While the proton-proton hydrogen fusion reaction (the same one that powers Main Sequence stars) is the hardest to “light,” and keep going, and be self-sustaining (while also “burning” fast enough to produce useful thrust while it’s still *in* the ramjet, as it’s notoriously slow), there is a possible alternative:

      Robert Forward designed hydrogen/antihydrogen rockets to power starprobes and starships, in which micrograms of antimatter hydrogen, mutually annihilating with equal amounts of hydrogen each second, would super-heat the remainder (nearly 100%) of the hydrogen to form a plasma, which would escape through a magnetic nozzle at tremendous velocities. While the performance of these antimatter rockets is very high, the fact that they must carry their own reaction mass limits their performance, BUT:

      This need not be an insuperable impediment. Instead of carrying tens, hundreds, or even thousands of tonnes of hydrogen fuel (and a tiny fraction as much mass of antihydrogen), a starprobe or starship might only need to carry a few tens, hundreds, or thousands of *grams* of antihydrogen, using hydrogen collected by a toroidal ramscoop as its reaction mass. Also:

      While the vehicle’s acceleration would be lower than that of a pure rocket, its acceleration would be higher than that of an equivalent proton-proton fusion ramjet (assuming a workable one could be built), and its range could be, for all practical purposes, unlimited. A few tonnes of antihydrogen, of which only micrograms (or less) would be needed each second for reacting (mutually annihilating) with the hydrogen collected by the ramscoop, should allow relativistic starflight across and all through the Milky Way.

  • ljk January 16, 2018, 12:31

    China wants to remove space debris in Earth orbit using a powerful laser. Could this be evolved into something useful for Breakthrough Starshot?


  • Michael Fidler January 19, 2018, 1:43

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