Q&A: Small solar sails could be the next ‘giant leap’ for interplanetary space exploration

Almost 70 years after the launch of the primary satellite, we nonetheless have extra questions than solutions about space. However a workforce of Berkeley researchers is on a mission to alter this with a proposal to construct a fleet of low-cost, autonomous spacecraft, every weighing solely 10 grams and propelled by nothing greater than the stress of solar radiation. These miniaturized solar sails may doubtlessly go to 1000’s of near-Earth asteroids and comets, capturing high-resolution photographs and amassing samples.

Led by Kristofer Pister, professor {of electrical} engineering and pc sciences, the researchers search to leverage developments in micro-scale expertise to make interplanetary space exploration cheaper and accessible—and to speed up new discoveries about our interior solar system.

They describe their work, the Berkeley Low-cost Interplanetary Photo voltaic Sail (BLISS) undertaking, in a research published within the journal Acta Astronautica.

The BLISS undertaking brings collectively researchers from the Division of Electrical Engineering and Laptop Sciences and the Division of Mechanical Engineering, in addition to the Berkeley Sensor and Actuator Heart and the Area Sciences Laboratory. Their work builds on different small spacecraft initiatives, together with CubeSats, ChipSats and the Breakthrough Starshot Initiative, whereas in search of to enhance solar sail maneuverability and additional cut back fabrication prices through the use of low-mass client electronics.

Along with Pister, the workforce consists of lead creator and mechanical engineering doctoral pupil Alexander Alvara and co-authors Lydia Lee, Emmanuel Sin, Nathan Lambert and Andrew Westphal.

In a latest dialog, Pister and Alvara shared their group’s imaginative and prescient for this undertaking with Berkeley Engineering.

Your newest paper focuses on fleets of small solar sails. What benefits do solar sails have over different forms of spacecraft?

Alvara: Photo voltaic sails use a non-consumable propulsion power. They’re propelled by daylight, just like how a sailboat is propelled by wind. So, not like different spacecraft, solar sails can journey across the galaxy, or, extra particularly, our solar system, with out having to hold any gasoline or fear about refueling.

Pister: The magic is that mild, though it does not have mass, has momentum. When mild bounces off a mirror, you get a power as a consequence of that change in momentum. And on a sq. meter sail, that power is tiny. It is concerning the weight of a grain of sand, however you get it without spending a dime. And also you get it for so long as you need, so long as you are sitting in space with the daylight putting you.

Might you inform us concerning the Berkeley Low-cost Interplanetary Photo voltaic Sail, or BLISS, undertaking? What was the genesis of this undertaking and what are its objectives?

Pister: It began a number of years in the past, when pals of mine have been exchanging emails about an object, referred to as ‘Oumuamua, that was transferring by means of our solar system. Some individuals have been saying that possibly it is an alien solar sail, after which [physicist] Dick Garwin despatched round a paper that he had written in 1959 about solar sails.

It stated that you should use this mild stress to maneuver out, away from the sun, which is sensible—the sunshine pushes in that path. However you may as well use it to maneuver in. It is sort of like tacking towards the wind in crusing. Mild is way more like wind, and you may tack utilizing solar radiation stress.

So this lightbulb went off in my mind. All of the work we do in my group is targeted on miniaturizing issues, and I assumed we may miniaturize a solar sail spacecraft. Seeing you can tack towards mild stress made me understand that we may make spacecraft [weighing] 10 grams with virtually all off-the-shelf expertise. And our newest research gives proof that that is possible.

Our preliminary objective for the BLISS undertaking was easy: Seize photographs of all of the near-Earth asteroids, beginning with the largest ones. Roughly a thousand near-Earth asteroids are larger than a kilometer in diameter. And we’ve got footage, often fuzzy footage, of possibly 10 of them. We have been excited by the concept you can doubtlessly take an iPhone digital camera, orbit round considered one of this stuff, take a thousand high-resolution colour pictures from a really shut distance after which beam that data down.

Talking of miniaturizing issues, why make the solar sails small within the first place?

Alvara: A smaller measurement permits the spacecraft to be extra agile. We do not have to fret about buckling of the sail, which is only one sq. meter. This can be a large difficulty with bigger solar sails. Think about taking a solar sail that’s 50 sq. meters into space, then having unfolding parts spreading out like origami. It is nonetheless comparatively small in comparison with different spacecraft, however the unfolding parts add weight. And, as Kris talked about, you are getting the power of a grain of sand constantly in your sail, the sunshine stress, so that you need to have a solar sail near that mass. You do not need one thing that is large, or it should take without end to maneuver, and it should be much less simple to maneuver.

Pister: Price is one other benefit to going small. We’re proposing to start out at about 10 grams for an interplanetary spacecraft. If we do all the pieces proper, the price of the solar sails will likely be a thousand {dollars} or much less. We may then put 1000’s of those tiny spacecraft in just a little package deal, the scale of a small satellite, and launch them into space.

Alvara: So, for the price of a single launch, we may ship out 1000’s of those solar sails and attain a number of missions.

These spacecraft will have to be extremely practical but additionally mild. How will they not be weighed down by all of their parts?

Pister: We’re leveraging all of the expertise, all of the miniaturization and low energy consumption that goes into the design of cell telephones. However there are additionally many different devices that MEMS [microelectromechanical systems] has managed to miniaturize.

The BLISS spacecraft makes use of a MEMS system referred to as an inchworm motor. What’s an inchworm motor and why is it vital?

Alvara: You’ll be able to consider an inchworm motor as one thing that takes electrical energy and turns right into a moveable power. Nearly like a piston. We use the inchworm motor to seize onto issues, on this case, issues which can be a lot bigger than itself, and transfer it backwards and forwards.

Pister: Our little spacecraft has roughly a 1/2 meter diameter, super-lightweight mirror—possibly the scale of a card desk—that’s linked to the physique of the spacecraft by a number of carbon fiber filaments. The inchworms inch their method alongside these filaments, pulling on the filaments and transferring the sail relative to the middle of mass of the spacecraft. It seems that is what you’ll want to navigate—similar to on a sailboat. You pull on the strains and alter the perspective of the sail by means of the wind, and that impacts path.

How will these spacecraft navigate the interior solar system?

Alvara: The vast majority of the evaluation is completed utilizing one thing referred to as the Misplaced in Area [Identification] Algorithm. The concept is that you just map the celebs you can see, then evaluate them to the pixels of the photographs you can get out of your on-board cellular phone digital camera. So we will principally use smartphones to assist navigate.

There are various hazards in space, together with ionizing radiation and huge floating particles. How do you design the tiny solar sails to resist these potential risks?

Alvara: A whole lot of work has already been completed analyzing off-the-shelf components which have endured space-like radiation. To mitigate such hazards, we will both construct in redundancy and add a number of parts which have the best probability of failure, or pair these BLISS spacecraft in what we name accomplice constellations, which principally provides redundancy for us.

Might you inform us concerning the idea missions that you have proposed for BLISS spacecraft? How lengthy wouldn’t it take to finish these missions?

Alvara: Kris had talked about earlier sending the solar sails to discover near-Earth asteroids. One of many different major idea missions is cometary pattern retrieval, so getting microdust from comet plumes. So far, there’s been just one actual profitable return of cometary materials, and that was the Stardust mission within the early 2000s.

It did a flyby of a comet referred to as Wild 2 and picked up materials and introduced it again to Earth. However sadly, the spacecraft was much less maneuverable than they anticipated, and it caught the comet dust particles at excessive velocity, vaporizing any organic-rich parts within the pattern. Although the pattern they retrieved was nonetheless vastly vital, we presently have solely about 300 micrograms of comet materials on Earth. And by designing our tiny solar sails to be agile and extremely maneuverable, we hope to seize cometary samples at low relative speeds to keep away from damaging any organics.

Pister: As for the mission durations, they fluctuate so much. It should take us some variety of months to get out of Earth’s orbit, it should take us months or years to get to the asteroid or comet that we’re occupied with, after which the reverse of that coming again in. So, actually months on the quick finish, and possibly a decade or so on the lengthy finish.

How far off are we from the primary launch?

Alvara: We may feasibly do it in a number of years. For instance, CubeSat initiatives often come out of excessive colleges or group school or four-year establishments, from undergrads. And people go from zero to launch in about two years. So with grad college students, post-docs or research scientists on the job, who’ve been doing this kind of factor for a few years, we must always be capable to launch inside that very same timeline as soon as we full improvement.

Pister: Thus far, Alexander’s labored on a few of the theories and a few of the motors. However there are six different techniques and all types of software program nonetheless wanted, so it could be an enterprise. However I am hopeful that we will receive funding for additional analysis.