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Star Travel and the Interstellar Medium, particle effects

The interstellar medium - the coronal gas - forms a column between locations in space. The sun is 4 light years from one edge of a 60 light-year-across cloud with a density of 0.3 hydrogens per cubic centimeter, or 3e5 H/m3, encountering the sun as it moves towards Scorpio at 25 km/s. Around that cloud is the Local Bubble, 300 LY across with a density of 50 H/m3. A light year is 9.5e15 meters, so for the first 4 light years in one direction, and more than 50 LY in the opposite direction, we encounter a column of hydrogen atoms with a density of about 1e21 H/m2-LY. That is the density of a layer of liquid water 30 nm thick per light year. 100 light years, 3 micrometers.

These protons will implant themselves in the surface of any object passing through them. At a mere 25 km/s, the energy per proton is 3.6 electron volts - many will bounce off. Approaching the speed of light, the energy approaches multiples of the mass energy of the proton, 938 MeV/c2. That will damage solid structure to the implant depth.

I don't know how much. A particle physicist can tell you how deep.

Conditions in Local Cloud, 3e5 H/m3, 5e-22 kg/m3 as perceived from moving frame

speed

v/c

1\over{c^2-v^2}

energy

flux

Pressure

m/s

1/m2-s

Pascals

25k

8e-5

1

4 eV

8e9

30k

1e-4

1

5 eV

9e9

100k

3.3e-4

1

50 eV

3e10

300k

1e-3

1

500 eV

9e10

14μ

1M

3.3e-3

1

5 keV

3e11

500μ

1.4M

5e-3

1

10 keV

4e11

1.4m

low energy ion implantation

3M

1e-2

1

50 keV

9e11

14m

low energy van Allen belt

4.2M

1.4e-2

1

100 keV

1.3e12

37m

6000x more flux than 100 keV van Allen belt

10M

3.3e-2

1

500 keV

3e12

0.5

high energy ion implantation

14M

4.2e-2

1

1 MeV

4e12

1.4

2e5 more flux than 10 MeV van Allen belt

30M

0.10

1.01

5 MeV

9e12

14

7 W/m2 particle power

100M

0.33

1.13

50 MeV

3e13

570

200M

0.67

1.80

380 MeV

8e13

7K

highest energy van Allen belt, 1e12 more flux

250M

0.83

3.28

500 MeV

1.4e14

26K

11 KW/m2 particle power

https://upload.wikimedia.org/wikipedia/commons/7/74/Local_Interstellar_Clouds_with_motion_arrows.jpg

InterstellarMedium (last edited 2015-10-14 02:24:00 by KeithLofstrom)