Re: starship-design: LINAC efficiency

[Steve VanDevender <stevev@efn.org>]

KellySt@aol.com writes:
 > And again, our analysis here was that you couldn't scoop up as much mass as 
 > the mass of the scoop over any nearby mission.

You would need a large scoop cross-section, but it's not inconceivable.

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.

This is all just back-of-the-envelope calculation, of course, but it's
clearly an indication that you'd need a very large ramscoop to make a
reasonably-sized ship work.