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Mission to an Interstellar Asteroid

On the matter of interstellar visitors, bear in mind that our friend ‘Oumuamua, the subject of yesterday’s post, was discovered at the University of Hawaii’s Institute for Astronomy, using the Pan-STARRS telescope. The Panoramic Survey Telescope and Rapid Response System is located at Haleakala Observatory on Maui, where it has proven adept at finding new asteroids, comets and variable stars. Consider ‘Oumuamua a bonus, and according to a new paper from Greg Laughlin and Darryl Seligman (Yale University), a type of object we’ll be seeing again.

Pan-STARRS may find objects like this every few years, but we’ll get a bigger payoff in terms of interstellar wanderers with the Large Synoptic Survey Telescope (LSST), now under construction at Cerro Pachón (Chile). Laughlin and Seligman think that this instrument will up the discovery rate as high as several per year, allowing us to see ‘Oumuamua in context, and also, perhaps, setting up the possibility of an intercept mission with a kinetic impactor.

More on that in a moment. But first, it’s interesting to see theories about its place of origin springing up in the brief interval since ‘Oumuamua’s passage. One of the stars of the Carina/Columba association (165-275 light years from Earth) is suggested, as is the double star system HD 200325. One recent survey of more than 200,000 nearby stars could find no conclusive evidence, but does suggest that 820,000 years ago, ‘Oumuamua encountered Gliese 876. There is even a possibility, which Laughlin and Seligman dismiss, that the object originally was ejected from our own Solar System and has now had a new encounter with it.

But back to a potential mission to ‘Oumuamua. What the authors have in mind is a kinetic impactor, which has the great advantage of producing a debris plume that we could look at with a spectroscope. We have a history of comet exploration dating back to Comet Giacobini Zinner in 1985 (International Sun-Earth Explorer), the flurry of missions — Giotto, Vega 1, Vega 2, Sakigake, Suisei — that investigated Comet Halley in 1986, the Deep Space 1 mission at Comet Borrelly (2001), and Stardust at Comet Wild 2. And the, of course, there is Deep Impact, a kinetic impactor that struck Comet Tempel I, and the European Space Agency’s highly successful Rosetta at Comet 67/Churyumov-Gerasimenko.

Even now we have the Osiris-REx mission enroute to the asteroid Bennu on a sample return mission. Thus a mission to an object from outside the Solar System seems feasible, though the challenges are obvious. As the paper notes:

Such a mission would face a number of challenges, including (1) the large heliocentric velocities of objects on hyperbolic trajectories, and (2) the lack of substantial time following the discovery of the target object for mission planning and execution, and (3) uncertainty in targeting during final approach. It is worth noting that when ‘Oumuamua was detected and announced in late October 2017, it had already passed its periastron location (which occurred on 9 September, 2017), and indeed, was already more than 1 AU from the Sun.

You may recall Andreas Hein and a team from the Initiative for Interstellar Studies, who have explored potential rendezvous missions to ’Oumuamua (see Project Lyra: Sending a Spacecraft to 1I/’Oumuamua). Laughlin and Seligman consider their mission as complementary to Hein and team, assessing how to investigate an interstellar object using chemical propulsion. Like Deep Impact, the actual impactor would be accompanied by a companion flyby probe that would examine the results spectroscopically. The feasibility of such a mission depends on having sufficient lead-time to launch the interceptor to the incoming object on a hyperbolic orbit.

Lead time is considered here in terms of the expected arrival directions and speeds of such objects. The authors do this by assuming a kinematic distribution similar to Population I stars, bearing in mind that the number of interstellar asteroids may be as much as 1016 higher than the number of stars. The paper samples the distribution of such asteroids in a cube of 10 AU around the Sun, pinpointing where they would be detectable and for how long. Such knowledge would allow us to determine optimal interception trajectories.

Image: This is Figure 3 from the paper. Caption: A sky map showing the probability that a future interstellar asteroid will approach the Solar System on a trajectory parallel to that direction. The darker colors indicate a higher probability. The axes denote degrees from a heliocentric point of view and the ecliptic is plotted in black. The sky positions of the constellations Serpens and Lepus, which are close in proximity to the Solar apex and anti-apex respectively, are plotted for context. The black circle indicates the sky location that ‘Oumuamua entered our Solar System, consistent with the prediction that the majority of these objects will approach with velocities parallel to the galactic apex. Credit: Laughlin & Seligman.

I send you to the paper for the specifics, but do note this with regard to ‘Oumuamua. When it was discovered, the object was three weeks beyond periastron passage, making reaching it problematic. Putting their trajectory analysis methods to work on ‘Oumuamua, the authors find that with an earlier detection, interception of ‘Oumuamua would not have been out of the question. Future interstellar asteroids could be reached given early detection and favorable trajectories — in fact, the authors conclude that wait times for mission opportunities should be in the range of 10 years, once we have the LSST (scheduled for first light in 2021) available.

And these interesting specifics on a potential mission:

The SpaceX Falcon Heavy quotes a payload capability to Mars of 16,800 kg, which we conservatively use for the payload constraint to L1. The Deep Impact mission to Tempel I had an impactor weighing ∼ 400 kg and a scientific package weighing ∼ 600 kg (A’Hearn et al. 2005). Due to the uncertainty of the position of the ISO [interstellar object], it seems appropriate to use ∼ 16 impactors, with a total weight of 400 kg. The mission program is greatly assisted by the expected 40 km/s velocity of impact with the hyperbolic ISO. Assuming that the remainder of the payload consists of fuel and oxidants, to account for the oxidants and efficiency of the rocket, we allow ∼ 1200 kg of fuel (with specific energy similar to compressed hydrogen) to produce the ∆V. Equating the kinetic energy to the energy produced by the fuel, we calculate that a maximum ∆V ∼ 15 km/s should be attainable, to impart the same amount of kinetic energy (per impact) as the Deep Impact Tempel I interception did.

Image: This is Figure 7 from the paper. Caption: Trajectory of the minimum-∆V mission interception mission sent on July 25th 2017, which had a flight time of 83.38 days. The trajectories for ‘Oumuamua, the Earth, and the rocket are plotted in red, blue and grey respectively in four day intervals in the smaller circles, while the larger circles are plotted in 28 day intervals. The arrows indicate the positions in space of ‘Oumuamua and the rocket on the launch and interception date, 7/25/2017 and 10/16/2016. Projections in the X-Y, Y-Z and X-Z planes are shown in the left, right upper, and right lower panel respectively. Credit: Laughlin & Seligman.

16 impactors to an interstellar asteroid on a manageable trajectory, with the promise of spectroscopic analysis to equal those we have achieved with previous cometary missions. With a discovery rate ramping up to several per year once LSST is available, we should have targets to work with in the 2020s, helping us learn whether what we know of ‘Oumuamua is indicative of the population of these objects. The close-up study of remnants of planetary formation around other stars is now becoming possible provided we know where to look and when to launch.

The Laughlin & Seligman paper is “The Feasibility and Benefits of In Situ Exploration of ‘Oumuamua-like Objects,” accepted at the Astronomical Journal and available as a preprint.


Comments on this entry are closed.

  • Ron S. March 21, 2018, 13:59

    It strikes me that if cost were no object (ha!) it would be beneficial to have a small constellation of suitable spacecraft in various solar orbits so that there is a higher probability that one would have the position and velocity to achieve an encounter. Relying solely on Earth-based launches, confounded by unpredictable space agency priorities of the moment, could mean a long wait for a suitable interloper to appear.

    • Antonio March 22, 2018, 4:27

      The propellent would boil off while waiting for the asteroid.

      • J. Jason Wentworth March 23, 2018, 2:21

        In an earmarked launch vehicle, or in a kick stage (escape/intercept trajectory injection stage) of an “on alert” probe, neither solid propellant nor storable hypergolic liquid bi-propellant (nor storable mono-propellant, such as the mono-methyl hydrazine used in spacecraft attitude control and maneuvering [trajectory adjustment] thrusters) would boil off during the wait, and:

        The U.S. no longer uses storable hypergolic liquid bi-propellant launch vehicles such as the Titan III and IV (which were developed from the Titan II ICBM) and the Agena upper stage (and the Delta II’s second stage [the very last Delta II launch will occur this September]) due to these propellants’ toxicity, but these propellants remain popular for spacecraft use because the quantities involved are far smaller. The Russians, however, use numerous hypergolic propellant launch vehicles (developed from ballistic missiles, or actual retired missiles, adapted to launch spacecraft), some of which can be stored–with no maintenance required–in sealed launch canisters for decades before use. Such launch vehicles (as well as their newer, solid propellant ICBM-derived ones) could be used as “launch when needed” carriers of interstellar asteroid probes.

    • J. Jason Wentworth March 22, 2018, 9:41

      Something rather like this has already been done (and was proposed by Avco in the 1960s, too). Back then, they proposed launching Mariner 4-type spacecraft into the asteroid belt, to examine planetoids in flybys, and these probes would also investigate passing comets. Also:

      While ISEE-3 (International Sun-Earth Explorer-3, which was renamed ICE [International Cometary Explorer] for the occasion of its re-purposed mission to Comet Giacobini-Zinner) is a well-known example of such a “solar orbit ‘holding pattern’ mission” (it wasn’t just waiting there, of course), whose spacecraft was dispatched to a target of opportunity, it wasn’t the first:

      The Pioneer 7 solar probe was launched on August 17, 1966, and took up an orbit with an average distance of 1.1 AU from the Sun. Nearly 20 years later, on March 20, 1986, it passed within 12.3 million kilometers of Halley’s Comet and monitored the interaction between the cometary hydrogen tail and the solar wind, discovering He+ plasma produced by charge exchange of solar wind He++ with neutral cometary material, and:

      The Pioneer Venus Orbiter (launched on May 20, 1978) observed Halley’s Comet during February 1986–including at the comet’s perihelion on February 9, when it was un-observable from Earth–when it monitored the comet’s loss of water and took ultraviolet images of it. Both of these Pioneer spacecraft’s instruments were well-suited to examining the comet, even though they weren’t designed with comet exploration in mind. As well:

      Likewise, a follow-on series of solar-orbiting, Sun-monitoring probes (which would be beneficial for purely practical reasons, such as monitoring solar flares and coronal mass ejections, which affect electricity distribution and radio & television reception) could be placed on-station, carrying small, spin-stabilized sub-probes (equipped with solid propellant kick motors). These sub-probes could be launched toward interstellar asteroid targets of opportunity. In addition:

      Ultra-lightweight laser-propelled sail probes, of either the Earth-based laser-pushed Starshot type or Young Bae’s “photon recycling” Photonic Laser Thruster (PLT, see: http://en.wikipedia.org/wiki/Photonic_laser_thruster and http://www.sciencedirect.com/science/article/pii/S187538921202514X ) type, could be another (even complementary, rather than exclusive) way to have interstellar asteroid probes “in reserve” to explore these objects as they appear. With the very high velocities that such laser sail probes could reach, it should be possible to launch them (either from Earth orbit “storage,” or with a ready-and-waiting [or in “ready storage”] Minotaur IV [or Minotaur-C] launch vehicle) such that they would match–or nearly match–the interstellar objects’ velocities (at the desired rendezvous or slow flyby points). In addition:

      With the savage acceleration that a sail probe (especially a PLT sail probe) would experience, keeping its mass to an absolute minimum—and, if possible, “printing on/in” its circuits and sensors, as Robert Forward envisioned for his microwave-pushed Starwisp probe—would be one way to make them more survivable. Power supplies which are now being developed for terrestrial applications could be used for such probes:

      Thin-film alpha-voltaic and beta-voltaic radioisotope power systems (“flat RTGs,” see: http://www.google.com/search?source=hp&ei=SJCzWo3oE9OojwOKn6mgCg&q=radioisotope+thin-film+powered+microsystems&oq=thin+film+radioisotope&gs_l=psy-ab.1.0.0i22i30k1j0i22i10i30k1.1142.10748.0.16814.….0…1c.1.64.psy-ab..0.22.3144…0j0i131k1j0i8i13i30k1.0.-9kA9CmEWis and http://www.google.com/search?ei=WZCzWv2AK5PqjwPE85qwDQ&q=radioisotope+thin-film+power+microsystems+pdf&oq=radioisotope+thin-film+powered+microsyst&gs_l=psy-ab.1.1.0i22i30k1j0i22i10i30k1.44438.44966.0.48085.….0…1c.1.64.psy-ab..1.2.504….0.lCCW62Zlshw ) are under development for powering terrestrial electronic devices, and they could probably be adapted to power such “probes-printed-on-sails” spacecraft.

  • Charley March 21, 2018, 14:54

    You are anticipating that you can build the spacecraft, and have sufficient amount of propulsive energy to perhaps perform a rendezvous with this object?
    Computationally the entire problem is easily planned out and able to be mapped out, but computations don’t produce actual spacecraft to be designed, built, integrated with the launch vehicle, assemble, that the launch facility and placed on the pad. This would be in the realm of a realistic proposal if you’re interested in seeing what a asteroid looks like from deep interstellar space.

    It should be noted that this may be possible to accomplish this, but I’m very, very skeptical that there would be any ‘political Delta V’ that could be applied to this project that would cause the government to say yes, let’s do this because the scientists want to get a sample of an interstellar body.
    The question comes down to who’s going to pay for this and what will necessarily have to be sacrificed to allow this to be implemented and greenlighted. This should be planed for the next body that comes from deep space .

    • Jeff Wright March 21, 2018, 16:49

      This might be where science can benefit from the proposed Space Force. Years ago, there was a plan to put a TAV minispaceplane atop an SRB based launcher, housed in an ICBM like silo.

      Solids can be stored for years. Same with ampulized hypergolic upper stages.

      Here though, a transient even launch on warning scenario can be used to fire such an NGL/SRB based LV at a moment’s noticed, allowing a flyby of mst any object in the inner solar system with enough lead time. Milspace foots the bill, with a generic spacecraft bus or asteroid interceptor to be switched out for a HOT EAGLE like TAV.

  • Michael March 21, 2018, 15:40

    Perhaps a test impactor could be sent to Ceres to whip up some material which should easily make escape velocity, Dawn could observe the debris cloud spectrally if it is still active.

  • Andrew Palfreyman March 21, 2018, 16:57

    Beamers in both hemispheres would ensure that rendezvous or collision was almost always possible, using something perhaps a little heavier than StarShot’s StarChip.

  • Curious March 21, 2018, 19:35

    Would have been interesting to see the authors assess an all solid/storable propellant launch vehicle such as Minotaur IV. This has the significant advantage of being ready to go at a moments notice. Obviously you’d need to have the payload/impactor/sensor already at launch site ready to go. The cubesat community is steadily driving down the size and cost of sensors to point there are different possibilities today than there were even 5 years ago. For an example of that look at this presentation https://icubesat.org/papers/2017-2/2017-a-1-1-deep-space-cubesats-and-nanosats-at-jpl/ starting around minute 3:58. The combination of cubesat driven tech and lowering launch costs could usher in new opportunities to realistically consider launching many smaller yet fairly capable probes to maximize the overall data collection

  • Joy March 22, 2018, 2:01

    Ok, just for grins and giggles, imagine a starship with ice shielding, darkened and pitted by eons of travel. And we will welcome this visitor by launching a salvo of kinetic kill projectiles at it. Before we know what it is. What could go wrong?

    • ole burde March 22, 2018, 10:08

      No grins and giggles ….this unknown probability is just another reason to get exided about something ELSE , perhabs some of the empty areas on the practical-technology map such as rotational gravity and closed cycle agriculture

      • J. Jason Wentworth March 23, 2018, 6:19

        Not necessarily; a safe alternative (in the event an interstellar asteroid turned out to be “more than it seemed to be from afar”) to a penetrator would be a velocity-matching rendezvous or slow flyby probe. A small probe–or a number of them–could be dispatched at the correct velocity to match (or nearly match) the interstellar object’s velocity at a selected distance from the Sun, and:

        In addition to a “de-rated” Breakthrough Starshot-type laser-pushed lightsail probe, two other options are Young K. Bae’s “photon recycling” Photonic Laser Thruster (PLT, see: http://en.wikipedia.org/wiki/Photonic_laser_thruster ) sail, and Professor Fritz Zwicky’s little-known but successful sounding rocket-lofted, gun-launched projectile method (he used it to launch artificial meteors, but resin-“potted,” acceleration-hardened projectile probes could also be launched in this way [Gerald Bull’s later “Martlets”–instrumented suborbital space gun projectiles that he fired over 100 miles high–were also “potted”]). Also:

        On October 16, 1957 (after a misfired [probably due to a wiring error] initial attempt during an otherwise successful V-2 flight on December 17, 1946), the first human-made objects ever to escape from Earth were fired into space by short, smooth-bore shaped-charge guns carried in the nose of an Aerobee sounding rocket (see: http://www.drewexmachina.com/2017/10/16/fritz-zwickys-solar-orbiting-pellets/ ). One of the metal pellets–as Arthur C. Clarke noted in “The Promise of Space”–achieved a speed of 33,000 miles per hour, far in excess of escape velocity (and later rocket/gun-propelled artificial meteors reached over 40,000 mph). In addition:

        Cylindrical, cast-in-clear-resin projectile-probes could incorporate instruments, batteries (and/or solar sails), radio systems, and even “push broom” spin-scan cameras (like the one aboard the Juno probe) into the cast resin cylinder. (The final sounding rocket upper stage carrying the gun or guns could be spun, both to spin-stabilize itself and to impart spin to the gun or guns and their projectile-probes [multiple guns could be carried and spin-ejected from the rocket stage].) As well:

        This launching technique could also be utilized to launch low-cost lunar flyby and impact probes, solar orbit probes, comet and NEA flyby (including slow flyby) and impact probes, and suborbital space probes (also called geospace probes), which could also return meteoroid stream and comet particles samples to Earth. Space probes are defined as payloads or vehicles which rise to distances greater than 4,000 miles (one Earth radius); altitudes of up to millions of miles are possible for these “just shy of escape velocity” suborbital probes before they fall back to Earth. They could fly through meteor streams and comets (collecting the particles in aerogel material placed in one end of the cylinder), and be weighted to fall “bottom first,” with a “cast-in” (or on) ablative heat shield (which could be of rounded or blunt conical shape, on the bottom end of the cylindrical projectile-probe; a simple, deployable drag streamer [like those used on cluster bomb sub-munitions, and on some model rockets] might suffice for a slow enough Earth landing).

    • Michael C. Fidler March 23, 2018, 2:14

      Speak softly, and carry a big stick!

    • J. Jason Wentworth March 23, 2018, 3:26

      Having recently read Arthur C. Clarke’s novel “Rendezvous with Rama” (in which a quickly re-purposed Neptune probe, re-named Sita, shocked humanity when it–and its multiple ejected camera pods–showed the supposed interstellar asteroid to be a cylindrical alien spacecraft), that is a heart-breaking (and also potentially terrifying) possibility to contemplate! Imagine our horror if an impactor-carrying flyby probe showed–when the signal-delay time would likely have made it too late to command the impactor to miss–that the target was actually a derelict starship…or worse, an operational vessel (possibly a worldship carrying thousands of conscious or hibernating peaceful explorers, or refugees from a dying world)! Also:

      Any of these unexpected outcomes would be a tragedy, and such an occurrence might–depending on the circumstances–make a new enemy (one with unknown capabilities), who might retaliate with the relativistic equivalent of “concrete bombs” (even the impact of a “slow,” 0.12 c massive object like a Daedalus starprobe would devastate a large area of the Earth’s surface). If intelligent life is very rare, this would compound the tragedy, even if they didn’t attack us in revenge, and:

      How terrible it would be, if we accidentally slaughtered the last surviving members of the only other intelligent race we knew of, or–if they were explorers–if (via their brief distress message to their home world, before they died) we could never exchange insights, history, and knowledge with that race, because they hated us for killing their folk… While these are unlikely possibilities if other apparent interstellar asteroids are detected approaching or transiting our Solar System, they should not be ignored, and even the 0.2 c Breakthrough Starshot laser-pushed lightsail probes aren’t without risk to possible aliens, either at or beyond the Alpha Centauri system.

    • ljk March 30, 2018, 12:20

      And yet some folks still question the need for placing information packages on our deep space vessels.

      If an ancient and presumably inert alien probe wandered into our star system, I am sure more than a few humans would be very grateful if that craft carried some kind of information about itself which would show its intentions.

      I would like to think that a space vessel with a peaceful purpose would also carry data indicating to any finders either directly or indirectly its non-hostile nature. The mere presence of such a “greeting card” from the probe’s makers would hopefully show that the visitor is not an attack on the recipients.

      Yes, an information package could be a ruse, but if a vessel was deliberately sent into a star system to wipe out any of its inhabitants, I don’t think it is a huge stretch of logic to presume the craft would not bother to carry such information in the first place, since it would not wait for what would likely be a small contingent or even an unmanned craft to intercept it.

  • ljk March 30, 2018, 12:12

    More comets need exploring as well if we want to learn about the early Sol system:


  • ljk July 2, 2018, 13:03

    Large Synoptic Survey Telescope to look for potentially risky asteroids

    The Large Synoptic Survey Telescope, or LSST, currently under construction in Chile will search for asteroids that could pose threats to Earth, providing a chance to avert a collision. “If we combine LSST data with other astronomical surveys like Pan-STARRS and the Catalina Sky Survey, we think we can help reach that goal of discovering 90 percent of potentially hazardous asteroids,” writes Vanderbilt University postdoctoral researcher Michael Lund.