RE: starship-design: LINAC efficiency

[Steve VanDevender <stevev@efn.org>]

L. Parker writes:
 > > Let's say your scoop can pick up on average 1 hydrogen atom per cubic
 > > centimeter.  Over a distance of 4.3 light years, you can pick
 > > up about 7
 > > * 10^-5 kilograms of hydrogen per square meter of scoop area.  So to
 > > pick up 10^9 kg of hydrogen during that trip, for example,
 > > you'd need a
 > > scoop with an area of 1.5 * 10^13 m^2, or some 2000 km in radius.
 > 
 > Did I miss something? I thought the local interstellar medium had been
 > determined to be thinner than once thought - like only 0.1 atom per cubic
 > meter...

I have to admit the density figure of 1 atom H per cm^3 came off the top
of my head and may be old and inaccurate.

If it's 0.1 atom per cubic meter, then yeah, ramscoops will have huge
problems.