First test of Breakthrough Starshot interstellar probe highlights likely damage due to gas and dust

August 25, 2016 by Bob Yirka report

(Phys.org)—A small team of researchers at Harvard University who are part of the Breakthrough Starshot team has been testing the likely damage to an interstellar spacecraft traveling at approximately one-fifth the speed of light as it makes its way to the Alpha Centauri star system. As they note in a paper describing their testing and results, which was uploaded to the arXiv preprint server, such damage could be catastrophic, but they believe they have a solution.

Earlier this year, Russian billionaire Yuri Milner announced to the world that he wants to send a probe to the Alpha Centauri star system—he put up $100 million of his own money to get the ball rolling on what is expected to be a multi-billion-dollar effort. At the time of the announcement, Milner told the press that his team of advisors had identified 20 main challenges that would have to be overcome in order for such a mission to be a success. In this new effort, the researchers have addressed one of those challenges—assessing the likely damage to the craft due to space dust and gases, and offering solutions to the problem.

The preliminary working design of a able to travel at ∼0.2c is little more than a circuit board that has come to be known as a wafersat—it would be attached to a light sail that would be the target of a laser sent from Earth to push it during the initial part of the journey. The wavsat would be made mostly of graphite and quartz. Thus, the researchers focused the bulk of their testing on these two materials. They discovered that particles of hit by the craft would mostly come in the form of collections of heavy atoms rather than particles—those collisions would cause two problems. The first would be the creation of pits on the surface of the craft, which would result in loss of material (up to 30 percent of the entire craft might be lost).

The second problem is melting. If the craft were unlucky enough to run into something larger, however, the team expects the results would be partial or complete destruction of the craft—but they believe the odds of that happening are small enough to make the project viable. Barring such a collision, the researchers believe that coating the front of the craft with a buffer would be enough to ensure its safe arrival to the Alpha Centauri star system approximately 20 years after launch.

Breakthrough Starshot Animation (Clip)

Explore further: Stephen Hawking joins futuristic bid to explore outer space (Update)

More information: The interaction of relativistic spacecrafts with the interstellar medium, arXiv:1608.05284 [astro-ph.GA] arxiv.org/abs/1608.05284

Abstract
The Breakthrough Starshot initiative aims to launch a gram-scale spacecraft to a speed of v∼0.2c, capable of reaching the nearest star system, α Centauri, in about 20 years. However, a critical challenge for the initiative is the damage to the spacecraft by interstellar gas and dust during the journey. In this paper, we quantify the interaction of a relativistic spacecraft with gas and dust in the interstellar medium. For gas bombardment, we find that damage by track formation due to heavy elements is an important effect. We find that gas bombardment can potentially damage the surface of the spacecraft to a depth of ∼0.1 mm for quartz material after traversing a gas column of NH∼2×1018cm−2 along the path to α Centauri, whereas the effect is much weaker for graphite material. The effect of dust bombardment erodes the spacecraft surface and produces numerous craters due to explosive evaporation of surface atoms. For a spacecraft speed v=0.2c, we find that dust bombardment can erode a surface layer of ∼0.5 mm thickness after the spacecraft has swept a column density of NH∼3×1017cm−2, assuming the standard gas-to-dust ratio of the interstellar medium. Dust bombardment also damages the spacecraft surface by modifying the material structure through melting. We calculate the equilibrium surface temperature due to collisional heating by gas atoms as well as the temperature profile as a function of depth into the spacecraft. Our quantitative results suggest methods for damage control, and we highlight possibilities for shielding strategies and protection of the spacecraft.

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Jeffhans1
5 / 5 (4) Aug 25, 2016
So what if we have to launch 10 probes per system? Finding out how many make it and in what condition should tell us a ton about the interstellar medium that they pass through to get there. If we end up with 7 or 8 still working on the far end, they can work together to give us multiple divergent readings on the system.
rwooten
4 / 5 (4) Aug 25, 2016
Any chance these micro probes will be able to include a reasonably decent spectrometer and camera? I'd be pretty satisfied with life as a whole if i could just see a direct image of an extra solar rocky planet from its host system, in my life time. I guess a better question would be can these small probes fit the transmitters needed to send back images? As an artist by hobby I'm getting pretty sick of "artist impressions", and as an architect by profession I demand the engineers do the impossible.
TheGhostofOtto1923
4.4 / 5 (8) Aug 25, 2016
The array would work much better from a lagrange point or the moon and in a few decades may be easier to construct and operate there robotically than on earth. Such an array could also be tasked to power intrasystem transport, earning its keep.
enteroctopus
1 / 5 (8) Aug 25, 2016
Study of the earth and its neighborhood is a far better investment of money than sending what will be a seriously outdated probe (by the time it gets there) to a system that most probably has no chance of supporting terrestrial life. In the 20 years it takes to get to the system we will undoubtedly have made great strides in earth-based and space-based systems capable of far more valuable data than a measly cellular phone camera would should it reach A. Centauri in 2036.

What have we learned since 1996? Where should I begin? Jupiter is way too hot, Pluto is not a planet, gravity waves exist (as probably do primordial black holes), etc. 1996 tech arriving at the star would be of limited interest to us today, aside from giving us the existential boner of getting something there.
LagomorphZero
5 / 5 (9) Aug 25, 2016
enteroctupus: using old technology doesn't make the data less valuable. We're still learning with voyager signals 40 years later.
bruenor
3.7 / 5 (3) Aug 25, 2016
I agree with Otto and am wondering why use an earth based laser.
The beam losses from atmosphere and periodic beam losses from the rotation of the earth must be worth considering.
Unless it is a raw power issue.
Could be an interesting analysis to see, there are enough brains on board, surely they have thought this through and it's the lack of good explanation.
Zorcon
4.5 / 5 (8) Aug 25, 2016
In the 20 years it takes to get to the system we will undoubtedly have made great strides in earth-based and space-based systems capable of far more valuable data....

1996 tech arriving at the star would be of limited interest to us today...


Almost everything we know about Pluto, we just learned from a fly-by probe that took 10 years to get there. It used 1990s technology.
Nik_2213
4.5 / 5 (4) Aug 25, 2016
Didn't they read the British Interplanetary Society's famous 'Daedalus Report' ? That covered stuff like this, needing multi-layered bump-shields in deep space, and a talc-fine 'dust-cloud' dispersed ahead of the main craft and its sub-probes during the fly-by...

The alternative is to shrug and send many, many 'star-wisps', in the hope a few get through. FWIW, I'd be happier with such mega-lasers if they were on the Lunar far-side, without 'line of sight' to Earth. Wouldn't want their targeting to be hacked...
antialias_physorg
5 / 5 (5) Aug 26, 2016
I agree with Otto and am wondering why use an earth based laser.

If you look at the amount of stuff we've put into space (especially weight issues) then an Earth based laser is a must. We just don't have the tech to put multi-gigawatt powerplants (and sizeable laser installations) into orbit just yet.

The beam losses from atmosphere and periodic beam losses from the rotation of the earth must be worth considering.

Beam losses are an issue, but rotation not so much because the starshot only accelerates the craft for 10 minutes.
https://en.wikipe...Starshot

Find sails that can withstand that kind of acceleration without ripping at the tiniest imbalance is going to be tricky.

Back of the envelope calcs give me an acceleration of 30000g. That seems like an awful lot.

TheGhostofOtto1923
4 / 5 (6) Aug 26, 2016
If you look at the amount of stuff we've put into space (especially weight issues) then an Earth based laser is a must. We just don't have the tech to put multi-gigawatt powerplants (and sizeable laser installations) into orbit just yet
We are approaching a revolution in space-based robotic construction.
A project such as this could be used to establish the capability just as the ISS was. This includes the potential for large nuclear reactors in space, a necessity for facilities in the outer system.

Given the time and money needed to be spent on getting regulatory approval of such a system on earth, a space array might actually happen faster.

You'll note also in the video that earth designs need hefty structures to support reflectors against gravity. Microgravity structures will be much simpler and ultimately cheaper to build. They could be modular design, fabric and foil material, and assembled, operated, and maintained robotically and autonomously.
TheGhostofOtto1923
4 / 5 (6) Aug 26, 2016
And given the potential for profit we could see this capability in a decade or 2.

"SpiderFab could help build big radio antennas, spacecraft booms and solar arrays in the next decade or so, said Rob Hoyt, CEO and chief scientist of Tethers Unlimited. But he has an even grander vision for the technology (and associated projects the company is working on) over the long haul. [Visions of the Future of Human Spaceflight]

"Our really long-term objective for all of this work is to eventually enable the use of in-situ resources to construct the infrastructure in space needed to support humanity's expansion throughout the solar system," Hoyt said March 4 during a presentation with NASA's Future In-Space Operations (FISO) working group."
torbjorn_b_g_larsson
5 / 5 (2) Aug 26, 2016
If you look at the amount of stuff we've put into space (especially weight issues) then an Earth based laser is a must. We just don't have the tech to put multi-gigawatt powerplants (and sizeable laser installations) into orbit just yet
We are approaching a revolution in space-based robotic construction.


It will still be much later than the Earth based, cheap, system can launch these probes. Since the closest potentially planet of Proxima b can be investigated by direct imaging, the need is not great, but the probes should improve data.

You'll note also in the video that earth designs need hefty structures to support reflectors against gravity.


Artistic license for lasers? The targeting system can be simple and co-position the lasers (by a weaker laser reflectance, say), so I don't grok the video suggested array look.
TheGhostofOtto1923
4.2 / 5 (5) Aug 27, 2016
The targeting system can be simple and co-position the lasers (by a weaker laser reflectance, say), so I don't grok the video suggested array look
Im not sure what co-position or weaker laser reflectance means. On earth or even on the moon youll need to compensate for rotation while tracking, which will require a substantial structure whether youre moving the laser/dish assembly itself or a secondary mirror. The whole thing will have to be weatherized and secured from intrusion. And this wont be cheap.

"Construction of the [square kilometer array] is scheduled to begin in 2018 for initial observations by 2020, but the construction budget is not secured at this stage. The SKA would be built in two phases, with Phase 1 (2018-2023) representing about 10% of the capability of the whole telescope. Phase 1 of the SKA was cost-capped at 650 million euros in 2013, while Phase 2's cost has not yet been established."
cont>
TheGhostofOtto1923
4.3 / 5 (6) Aug 27, 2016
-And as youre projecting energy through the atmosphere additional safety systems would need to be installed.
It will still be much later than the Earth based
-And as I say because of the unique nature of the system and the public perception of danger, the regulatory process itself could take decades.

In contrast a space-based array would need no extensive regulatory approvals. It would be much simpler structurally and would have no limit on acreage. A secondary tracking mirror for instance could be located kilometers away.

And it could pay for itself by providing power for transport throughout the system. A ground-based system couldnt do this because of the amount of energy needed to be transmitted through the atmosphere and the limited coverage and targeting capability.

And yes we are on the verge of building such megastructures as this in space. Only about 20 years between the first high power transmission lines and widespread regulated electric utilities.
TheGhostofOtto1923
4.2 / 5 (5) Aug 27, 2016
-And as it often happens when otto does a little research he discovers he is right.

Here is a vid of a talk by

Philip Lubin, Univ. of California Santa Barbara, DEEP IN Directed Propulsion for Interstellar Exploration

-explaining what the people who are actually working on this system are proposing. And yes its space-based.
http://livestream...05034354

-And it can be used for transport to mars in a few days as well as orbital debris mitigation and even terraforming.

And he uses the timeline of computer proliferation as a model for system development and cost.
TheGhostofOtto1923
4.2 / 5 (5) Aug 27, 2016
Heres another link
http://www.deepsp...ecursors

-with a simulation of a probe launched from low earth orbit;

"Example of Spacecraft Propelled by Laser
Consider a 10 g payload attached to a 2 m diameter sail (left) and a 1 g payload attached to a 0.7 m sail. The bare spacecraft mass is equal to the sail mass (right). In this example of a small system the laser array propelling the craft has an optical power of 272 kW and is 20 m diameter. The laser and craft both start in low Earth orbit. The array remains in low Earth orbit while the craft is slowly propelled away, spiraling outward from the Earth."
carbon_unit
1 / 5 (2) Aug 27, 2016
How the heck do we ever hear back from these things? What sort of radio/laser transmitter at Proxima b would it take to be receivable back here in the solar system with current technology? Quite a bit of power, I would bet. I'm not sure 3 decades of advances can produce a transmitter capable of interstellar communications that weighs only a few grams.
TheGhostofOtto1923
4.2 / 5 (5) Aug 27, 2016
How the heck do we ever hear back from these things? What sort of radio/laser transmitter at Proxima b would it take to be receivable back here in the solar system with current technology? Quite a bit of power, I would bet. I'm not sure 3 decades of advances can produce a transmitter capable of interstellar communications that weighs only a few grams.
As you might imagine the people working on the project have considered this.

Instead of asking here and expecting someone to look it up for you, why dont you do it yourself? Try the links I posted.
bruenor
2.5 / 5 (2) Aug 27, 2016
I think Unit may have been speaking rhetorically

Nice links though Otto ;)
gkam
1.1 / 5 (7) Aug 30, 2016
Parroting back the words of others does not signal a thorough understanding or even a superficial understanding of the issue.
TheGhostofOtto1923
4.5 / 5 (6) Aug 30, 2016
Parroting back the words of others does not signal a thorough understanding or even a superficial understanding of the issue.
Yeah much better to lie about your education and experience and then just make the facts up yourself. Much harder to disprove.

Except when everybody knows youre a lying cheating psychopath, then everybody just laughs and goes away.
Estevan57
5 / 5 (4) Aug 30, 2016
Well, Gkam, Otto does add his own thoughts and opinions on the subject, which you don't seem to be able to do.

Does it bother you that Otto converses with others here? It seems like it.

What do you think of building it at a Lagrange point?

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