Re: starship-design: Timothy's beamed power paper

[KellySt@aol.com]

In a message dated 7/22/97 7:51:15 AM, jimaclem@juno.com wrote:

>On Tue, 22 Jul 1997 14:35:54 +0200 (MET DST) Zenon Kulpa
><zkulpa@zmit1.ippt.gov.pl> writes:
>
>>> Something just occurred to me (again) in light of recent discussions 
>>
>>> regarding the impact of interstellar hydrogen on the sail, it seems 
>>to 
>>> me that there is a "terminal velocity" where the pressure from the 
>>> photons impactine the back of the sail will exactly balance the 
>>pressure 
>>> of the hydrogen impacting the front of the sail at relativistic 
>>> velocities. This point is probably well short of the speed of light 
>>> which would severely limit the usefuleness of sails. I can't recall 
>>> having seen any calculations along these lines. Anyone care to 
>>comment?
>>> 
>>That seems an important observation.
>>My guess is that even more restrictive on the sail speed
>>would be the physical damage inflicted on the sail by the 
>>interstellar medium (even the hydrogen atoms, but also other debris,
>>like dust). You cannot shield the entire sail...
>>
>>-- Zenon
>
>Good points, reminds me that the Bussard Ramjet was  expected to have the
>same drawback with drag interaction between the scoop field and the dust
>and gas.

I beleave it was thought the drag would always exceed the thrust.  <bummer>

Kelly