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 inside one edge of a 60 light-year-across Local 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. The table below (from Janni 1966) shows stopping range in silicon extrapolated by gram density to glass and water - perhaps poorly.

The numbers below are estimates - real measurements needed!

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

speed

v/c

1\over{c²-v²}

energy

flux

Stopping Range est mm

Pressure

m/s

1/m2-s

SiO₂

H₂O

Pascals

25k

8e-5

1

4 eV

8e9

30k

1e-4

1

5 eV

9e9

100k

3.3e-4

1

50 eV

3e10

1.1e-3

2.8e-3

300k

1e-3

1

500 eV

9e10

3.3e-3

8.5e-3

14μ

1M

3.3e-3

1

5 keV

3e11

1.6e-2

4.1e-2

500μ

1.4M

5e-3

1

10 keV

4e11

2.5e-2

6.5e-2

1.4m

low energy ion implantation

3M

1e-2

1

50 keV

9e11

0.08

0.2

14m

low energy van Allen belt

4.2M

0.014

1

100 keV

1.3e12

0.15

0.4

37m

100 keV van Allen belt, 6000x more flux

10M

0.033

1

500 keV

3e12

0.6

1.6

0.5

high energy ion implantation

14M

0.042

1

1 MeV

4e12

1.2

3.1

1.4

1 MeV van Allen belt, 2e5 more flux

30M

0.10

1.01

5 MeV

9e12

4.4

1.2

14

7 W/m2 particle power

100M

0.33

1.13

50 MeV

3e13

37

95

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.jpghttps://www.spenvis.oma.be/help/background/soldam/sprcp.gif

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