Cruise | Interstellar dust

Based on estimates of the density of dust in the local interstellar medium, over the course of a journey to Alpha Centauri each square centimeter of the frontal cross-sectional area of the StarChip and lightsail would encounter about 1,000 impacts from dust particles of size 0.1 micron and larger. However, there is only a 10% probability of a collision with a 1 micron particle, and a negligible probability of impact with much larger particles.

A 0.1 micron dust particle moving at 20% of the speed of light would penetrate and melt the StarChip to a depth of order 0.4mm. To estimate scale effects, calculations were made assuming a 10cm X 0.1mm thickness. Traveling with the nanocraft’s edge facing parallel to the velocity vector would reduce the cross section to 0.1cm2, for a 10 cm StarChip with a 0.1mm thickness. A protective coating of beryllium copper could be added to the leading edge of the StarChip, as a sacrificial layer for additional protection from dust impacts and erosion. If needed, the StarChip geometry could be elongated (‘needle’ geometry), to further minimize the cross-section.

To mitigate the impact of dust further the sail could potentially be folded into a streamlined configuration during the cruising phase to Alpha Centauri. This would minimize the frontal area of the sail. The nanocraft’s electronics could also be designed so as to be less vulnerable to localized damage from dust.

The momentum kick from 0.1 micron dust particles is small, and its effect on the nanocraft’s trajectory might be compensated for by photon thrusters.

Jul 25, 2016 03:25 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Jul 11, 2016 20:36 Wayne Blackburn Posted on: Breakthrough Initiatives:

"Has any consideration been given to how much momentum transfer between the Starshot probes and all of the matter between the stars? In other words, completely without respect to any damage done to the sail or even the package, will it have enough momentum to push through the interstellar medium and actually REACH its goal?"


First read attachment below.

If all particles stop in the sail we get less than 1ppm change in nanosat velocity. However, particles on 15 nm sail will perforate the sail and not stop and thus transfer less than 10-3 of momentum, resulting on a change in nanosat velocity of less than 1ppb.

– Sasha Buchman, Breakthrough Initiatives

Jul 25, 2016 03:30 Breakthrough Initiatives Posted on: Breakthrough Initiatives

Apr 13, 2016 06:29 David Theil Posted on: Breakthrough Initiatives:

"Why do we care about the sail after the boost phase? As long as it doesn't have a high liklihood of interfering with the probe function, who cares if it gets holed by dust? It is only impacts to the probe itself we care about.
Need to do modeling to see what happens when sputtered with relatively massive high energy particles. If each particle creates a 0.4mm sized crater, and the total surface area is roughly the size of 625 such craters, making the protective layer 1mm thick will likely keep the functional innards intact through 1000 collisions. (Some will have bad luck to be hit in the same place too many times, but some won't. This is a yield calculation)"


Yes to first part, see my comment above.
The 0.4 mm assumes the entire 5 mJ energy is used for melting something like silicon. You are correct that more modeling is needed to confirm the model. Testing in the lab might be difficult 5 mJ=30 PeV. Shielding and aspect ratio of chip also need modeling and optimization.

While interesting suggestions, deflection by electric and/or magnetic fields as well as charging by UV will be not practical due to the high relative velocity of the dust particles.

– Prof. Sasha Buchman, Breakthrough Initiatives

Jul 26, 2016 07:40 michael.million@sky.com Posted on: Centauri Dreams

'While interesting suggestions, deflection by electric and/or magnetic fields as well as charging by UV will be not practical due to the high relative velocity of the dust particles.'

Interstellar dust can have a high charge build up in the tens of eV, they can also have a high charge to mass ratio, we could do some calculations to determine how big an effect it would have on deflection of dust due to a high space craft charge on the leading edge of the disc. Not sure if rotating the charged disc would last long enough (drag dependant) to generate a magnetic field that would add to the deflection process of gas and dust.

Aug 25, 2016 13:27 michael.million@sky.com Posted on: Centauri Dreams

Work by T Hoang, A. Lazarian, B Burkhart and A Loeb indicate that a highly charged sail will not deflect charged dust particles very well, but if the charged sail is edge on the deflection radius now becomes larger than profile of the sail for the most part. Also larger edge on sails can hold larger charges with a smaller increase in the profile aiding the deflection process.

http://arxiv.org/abs/1608.05284

Aug 26, 2016 11:43 william@theroses.me.uk Posted on: Breakthrough Initiatives

I posted on an earlier problem the possibility of supporting the sail with carbon nanotubes. I see now that the advantages would be twofold. Firstly it is strong but secondly it would melt a bit and some stealth planes already use this to heal. As this is the front of the sail it would not need to reflect and so any holes caused would melt the carbon which would hopefully - I'm not sure if it would work in space - heal the sail.

Aug 30, 2016 13:22 Nathan Bemis Posted on: Breakthrough Initiatives

As included in the Atmosphere Challenge section, I suggest to change the shape of the chip to a thin tube/needle "bullet example" to minimize space debris and dust collision risk. Or have the components aligned and the chip formed into a long thin stick. We are going to see another advance in chip technology too. Intel is releasing chips that claim are 10x more durable, much more faster, and do not use transistors. The structure holding the cells read and transfers the information instead.
You could have the sail operate like an umbrella, opened to receive the lasers then have it collapse/fold to lead and protect the nanocraft in addition to protection already included on the chip itself.
With the sail streamlined, dust impact protection would only need to be applied to the leading nose of the craft. Allowing the sail to be redeployed when needed since it should have not taken damage. Sail redeployment could be useful if there's a return plan, used to transmit data, and other purposes.
An idea for craft return: Perform an eventual "U-turn with thrusters perhaps?" and slowed with the laser array for recovery. If the chip is programmable enough, you can map a space grid to guide it to, from, and around objects and points of reference. If we figure out how to make it return and how to slow it, it can come to a stop and received at designated coordinates.
**Has there been a review of an approach to have a laser source on the craft itself? This way it will provide MUCH longer term laser propulsion, near zero atmosphere interference, and could be reliably accurate on the sail. The heat onto the sail won't be as intense and there won't be as much g-force demand on the sail once in space since the onboard laser/s provide the rest. Then once at desired speed, the laser/s can point ahead of the crafts path to divert dust and particles.
Could the LHC be an example to achieve relativistic speeds in space? Perhaps the laser light itself can be exploited inside of a mirrored device, in the same manner magnets propel particles in the LHC.

Nov 05, 2016 04:32 Breakthrough Initiatives Posted on: Breakthrough Initiatives

RE:
"Jul 26, 2016 07:40michael.million@sky.comPosted on: Centauri Dreams
'While interesting suggestions, deflection by electric and/or magnetic fields as well as charging by UV will be not practical due to the high relative velocity of the dust particles.' Interstellar dust can have a high charge build up in the tens of eV, they can also have a high charge to mass ratio, we could do some calculations to determine how big an effect it would have on deflection of dust due to a high space craft charge on the leading edge of the disc. Not sure if rotating the charged disc would last long enough (drag dependant) to generate a magnetic field that would add to the deflection process of gas and dust."

Answer:
These are indeed interesting and creative solutions to this problem. The nanocraft will certainly develop a charge over time. Spinning the craft is a useful idea. The biggest uncertainty at this time is the composition of the interstellar medium.

- Avi Loeb, Breakthrough Starshot

Nov 05, 2016 04:33 Breakthrough Initiatives Posted on: Breakthrough Initiatives

RE:
"Aug 25, 2016 13:27michael.million@sky.comPosted on: Centauri Dreams
Work by T Hoang, A. Lazarian, B Burkhart and A Loeb indicate that a highly charged sail will not deflect charged dust particles very well, but if the charged sail is edge on the deflection radius now becomes larger than profile of the sail for the most part. Also larger edge on sails can hold larger charges with a smaller increase in the profile aiding the deflection process.

http://arxiv.org/abs/1608.05284";

Answer:
These are certainly ideas that need to be applied to our problems.

- Avi Loeb, Breakthrough Starshot

Nov 05, 2016 04:33 Breakthrough Initiatives Posted on: Breakthrough Initiatives

RE:
"Aug 26, 2016 11:43william@theroses.me.ukPosted on: Breakthrough Initiatives
I posted on an earlier problem the possibility of supporting the sail with carbon nanotubes. I see now that the advantages would be twofold. Firstly it is strong but secondly it would melt a bit and some stealth planes already use this to heal. As this is the front of the sail it would not need to reflect and so any holes caused would melt the carbon which would hopefully - I'm not sure if it would work in space - heal the sail."

Answer:
Self healing structures are a good idea and we would need to pursue something along these lines to have a chance to survive the needed 20+ years of our trip. This is certainly an idea that need to be applied to our problem.

- Avi Loeb, Breakthrough Starshot

Nov 05, 2016 04:33 Breakthrough Initiatives Posted on: Breakthrough Initiatives

RE:
"Aug 26, 2016 11:43william@theroses.me.ukPosted on: Breakthrough Initiatives
I posted on an earlier problem the possibility of supporting the sail with carbon nanotubes. I see now that the advantages would be twofold. Firstly it is strong but secondly it would melt a bit and some stealth planes already use this to heal. As this is the front of the sail it would not need to reflect and so any holes caused would melt the carbon which would hopefully - I'm not sure if it would work in space - heal the sail."

Answer:
Self healing structures are a good idea and we would need to pursue something along these lines to have a chance to survive the needed 20+ years of our trip. This is certainly an idea that need to be applied to our problem.

- Avi Loeb, Breakthrough Starshot

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