# Re: New idea Laser launcher/scoop systems

```At 4:32 PM 3/8/96, Timothy van der Linden wrote:
>>Opps forgot to add the mass ration numbers.  :(
>>
>>Specific impulse
>> (exaust velocity)
>>                Speed 50,000,000 m/s (1/6 light
>>                speed)
>>                                              Speed 100,000,000 m/s (1/3 light
>>                                              speed)
>>   2,500,000 sec
>> (25,000,000m/s)
>>                7 to 1 mass ratio.
>>                                              55 to 1 mass ratio.
>>   2,000,000 sec
>> (20,000,000m/s)
>>                12 to 1 mass ratio.
>>                                              148 to 1 mass ratio.
>>   1,500,000 sec
>> (15,000,000m/s)
>>                27 to 1 mass ratio.
>>                                              785 to 1 mass ratio.
>>
>
>Kelly, how did you calculate these numbers?
>
>Tim

found the equation.

A.1 The rocket equation

The "rocket equation" tells you that
the ratio of rocket mass when full of fuel to rocket mass after
burning the fuel is:

m(i) / m(f) = exp ( dV / v(e) )

Where:
m(i)  = intial mass
m(f)  = final mass
dV    = velocity change (9000 m/s in this case)
v(e)  = exhaust velocity (4500 m/s in this case)

----------------------------------------------------------------------

Kelly Starks                       Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)

----------------------------------------------------------------------

```