[extropy-chat] unidirectional thrust

[Dirk Bruere]

Mike Lorrey wrote:

>--- Dirk Bruere <dirk at neopax.com> wrote:
>  
>
>>> 
>>>
>>>      
>>>
>>Then either:
>>a) There is a preferred reference frame and relativity goes out the 
>>window, or
>>b) This is a recipe for an over unity device.
>>
>>Take your pick.
>>    
>>
>
>No, Dirk. You don't know what over unity is.
>
>  
>
And you do not understand the implications of 'thrust against the 
vacuum, fixed stars' etc
If we consider a 1kg model car (thrust against the earth) we can convert 
(neglecting friction and air resistance) say 1MJ of onboard energy to KE 
resulting in an eventual speed of  around 1400 m/s

Let's assume that we have a really good motor that can do all this in 
ten seconds, for a power input of 100kW. Now, the acceleration is *not 
uniform* over this time - it starts high and then tails off as the 
deltaKE increases 

Mean acceleration over the first second is going from 0 to 447 m/s for 
an expenditure of 100kJ ie 447 m/s^2
Clearly, if it accelerated at this rate for ten sec then its final 
velocity would be 4470 m/s, and it would have a KE some 10MJ - but it 
doesn't because we have a fixed reference against which we are pushing - 
the Earth.

Now let's translate that to the magic motor that thrusts against 
space/universe/whatever.
It still accelerates to 447 m/s in the first second, but... why should 
it not continue at that acceleration? According to relativity one bit of 
space is the same as another - no preferred frame. So after ten sec with 
an expenditure of 1MJ we have a KE (if it hits something in our 
reference frame from which we launched it) of 10MJ

Sounds pretty over unity to me.

-- 
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org



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