I hadn’t planned the conjunction of the Breakthrough Starshot forum’s opening here on Centauri Dreams and the interesting news out of the NASA budget for 2017, but some things just fall into your lap. In any case, what happened in Washington makes a nice follow-up to yesterday’s post, considering that it calls up visions of fast probes to Alpha Centauri, and in a document coming out of the U.S. House of Representatives, of all things. As more than a few readers have noted, it’s not often that we hear interstellar issues discussed in the halls of Congress.
Call for a New Interstellar Study
The specifics are that space-minded John Culberson (R-TX), who has championed space exploration with abandon, has made sure that NASA will look at the possibilities of interstellar travel. Culberson chairs the House of Representatives sub-panel in charge of NASA appropriations, and the call for interstellar study comes in a report that accompanies the bill establishing the agency’s budget for the coming year. You can see the report as submitted by Culberson online. Let me quote the relevant paragraph. First, the statement of the problem:
Interstellar propulsion research.—Current NASA propulsion investments include advancements in chemical, solar electric, and nuclear thermal propulsion. However, even in their ultimate theoretically achievable implementations, none of these could approach cruise velocities of one-tenth the speed of light (0.1c), nor could any other fission-based approach (including nuclear electric or pulsed fission).
Now the call for study:
The Committee encourages NASA to study and develop propulsion concepts that could enable an interstellar scientific probe with the capability of achieving a cruise velocity of 0.1c. These efforts shall be centered on enabling such a mission to Alpha Centauri, which can be launched by the one-hundredth anniversary, 2069, of the Apollo 11 moon landing. Propulsion concepts may include, but are not limited to fusion-based implementations (including antimatter-catalyzed fusion and the Bussard interstellar ramjet); matter-antimatter annihilation reactions; multiple forms of beamed energy approaches; and immense ‘sails’ that intercept solar photons or the solar wind. At the present time, none of these are beyond technology readiness level (TRL) 1 or 2.
And finally, the course to follow:
The NASA Innovative Advanced Concepts (NIAC) program is currently funding concept studies of directed energy propulsion for wafer-sized spacecraft that in principle could achieve velocities exceeding 0.1c and an electric sail that intercepts solar wind protons. Over the past few years NIAC has also funded mission-level concept studies of two fusion-based propulsion concepts. Therefore, within one year of enactment of this Act, NASA shall submit an interstellar propulsion technology assessment report with a draft conceptual roadmap, which may include an overview of potential advance propulsion concepts for such an interstellar mission, including technical challenges, technology readiness level assessments, risks, and potential near-term milestones and funding requirements.
Notice a couple of things here. First, keying a major effort to a significant anniversary is interesting as a motivational driver. Hence the call for reaching the goal of a launch by the one-hundredth anniversary of the Apollo 11 landing. As noted in these pages at the time, Yuri Milner’s Breakthrough Starshot was announced in conjunction with another such milestone, the anniversary of Yuri Gagarin’s orbital flight. Humans love to link big ideas with major events in the past as a way of goal-setting and, I suppose, putting a new idea into a broader context.
Note as well some of the parameters. Culberson talks about a spacecraft reaching ten percent of lightspeed, while Breakthrough Starshot goes for twenty percent. And while Starshot focuses tightly on small sails driven by phased laser array, Culberson’s call to NASA incorporates propulsion concepts ranging from sails to antimatter and even Bussard ramjets. Moreover, the report makes a nod to fusion-based propulsion as studied by the NASA Innovative Advanced Concepts program (NIAC). NASA is called upon to submit a technology assessment within a year of the enactment of the budget bill.
Dr. Forward Goes to Washington
If any of this sounds familiar, it may be because the only other time interstellar flight was considered in the U.S. Congress at any level of detail was when Robert Forward made an appearance before the Subcommittee on Space Science and Applications of the House Committee on Science and Technology. That was in 1975, when interstellar flight was rarely discussed outside of science fiction magazines, and the work of scientists like Forward appeared largely at conferences where interstellar issues were only a small part of the proceedings. There was, of course, no Internet, and media attention was scant.
Forward’s “A National Space Program for Interstellar Exploration” was as ambitious as it gets, calling for the launch of automated probes to nearby stellar systems by the turn of the 21st Century, with manned exploration to commence a scant 25 years later. With a budget that today seems modest, Forward called for ‘a few million dollars a year’ during the initial study phase, climbing into the multi-billion dollar range as the program began launching its first automated probes. As always, Forward thought big, as witness this:
Development of man-rated propulsion systems would continue for 20 years while awaiting the return of the automated probe data. Assuming positive returns from the probes, a manned exploration starship would be launched in 2025 AD, arriving at Alpha Centauri 10 to 20 years later.
Image: Interstellar theorist Robert Forward, whose work on beamed propulsion began in the early 1960s.
All that is by way of placing Rep. Culberson’s call to NASA in historical context. What Forward didn’t have when he made his recommendations was an ongoing privately funded effort like Breakthrough Starshot to offer a parallel track of development. It would be fascinating to know how he would have played that card. Breakthrough Starshot aims to spend its $100 million endowment on shaking out the basic concepts involved in a sail mission to Alpha Centauri. Forward would have been all over its phased laser array concept and we’re the poorer for not having his insights, especially on the issue of Earth- vs. space-based deployment.
The parallels between Culberson’s report and the Starshot studies are interesting if only in that both make reference to Philip Lubin’s work at NIAC on beamed propulsion. Lubin (UC-Santa Barbara) is a major figure in the Starshot effort, but his work goes back several years at NIAC, and thus offers ideas to both projects. Moreover, the Starchip concept — a ‘nano-spacecraft’ — being studied by Breakthrough Starshot is heavily dependent on Mason Peck’s work at Cornell, which also has had NIAC support. So NASA can draw on NIAC.
In the broader sense, though, both NASA and Starshot owe their inspiration on the propulsion side to Forward and the many colleagues who developed the core ideas of beamed propulsion over the past fifty years. Beaming to a sail has long been under investigation, though never so publicly. In the near future, I’ll be publishing an extended take on the history of these studies and how we have arrived at today’s laser sail concepts.
Image: A beamed lightsail as envisioned by the space artist Adrian Mann.
Will NASA and Breakthrough Starshot duplicate each other’s efforts? It’s not likely given current funding constraints, and whether it’s based at MSFC Huntsville or the Jet Propulsion Laboratory, the NASA effort outlined by Culberson calls only for an assessment of an interstellar mission. But having interstellar flight’s new media prominence so prominently reinforced by its introduction into a Congressional report on the NASA budget can’t hurt as we launch a serious look at what it takes to reach Alpha Centauri. We’ll soon learn what kind of synergies may exist.
Forward’s presentation to Congress can be found in “A National Space Program for Interstellar Exploration,” Future Space Programs 1975, vol. VI, Subcommittee on Space Science and Applications, Committee on Science and Technology, U.S. House of Representatives, Serial M, 94th Congress (September, 1975).