
 United States Patent
 Patent number: 5,305,974
 Date of patent: Apr. 26, 1994
 Spaceship Propulsion by Momentum Transfer
Abstract
A propulsion system for spaceships wherein a first electromagnetic projectile
launcher(EMPL) accelerates "smart" projectiles into space and on appropriate
trajectories to rendezvous with a distant spaceship at some later time. The smart
projectiles stabilize themselves in space using a system of on board thrusters operated by
computers. Laser beams and radio transmissions are directed at the spaceship and are
monitored by sensors aboard the spaceship. Computers on board the spaceship determine any
necessary course corrections for the projectiles based upon the spaceship's sensor system.
Appropriate commands are radioed to the projectiles which execute the commanded maneuvers
to alter their trajectories. The spaceship carries a second EMPL and a nuclearpowered
electricity generating facility to provide electricity to operate the EMPL. The spaceship,
the second EMPL and the nuclear power facility are all rotated axially about the long axis
of the EMPL to provide both gyroscopic stabilization and also artificial gravity for the
crew of the spaceship. The second EMPL is used to catch the projectiles which transfers
the momentum of the projectiles to the spaceship thereby accelerating it in the desired
direction. Additional acceleration of the spaceship is achieved by again launching the
captured projectiles in a direction opposite to the desired direction of motion of the
spaceship. The spaceship can be decelerated in a similar manner. Mars can be reached in
two months using this system.
Fixed these links 02/23/01
Why is my propulsion system better?
Because the specific impulse of my propulsion system is at
least 3300 seconds and can be increased up to 10,000 seconds. Perhaps you don't know
what specific impulse is. Well, specific impulse is defined to be the ratio of the thrust
of the rocket to the weight flow rate of the propellant. When stated in this manner it is
difficult to understand. A simpler way to express it is the number of seconds that one
pound of propellant would burn while producing one pound of thrust. It is a measure of the
energy in the propellant.
The following is a table of specific impulses of various different propulsion systems.
 Specific Impulse Comparions
Propulsion system 
Specific Impulse (sec) 
LOXLH2 (space shuttle system) 
450  475 
OBeH (most energetic chemical propellant) 
705 
Augustine Engine 
900  1000 
Nuclear thermal rocket (fission) 

solid core 
500  1100 
liquid core 
1300  1600 
gas core 
3000  7000 
(*) Nuclear electric rocket 
800  30000 
Momentum exchange (my system) 
3000  10000 
(*) Ion drive (such as NASA Deep Space 1) 
3000  25000 
(*) Nuclear fusion rocket 
1,000,000= (.033c) 
(*) Antimatter rocket 
28,775,000=(.94c) 
(*) Photon drive (light beam) 
30,000,000= (1.0c) 
The problem with all systems marked by (*) is that their total thrust is very low. Take
the Ion drive used by the Nasa Deep Space 1 project. Its total thrust is measured in
ounces (see Popular Science, 7/98, p.44) These systems are therefore useless
for transporting people to distant planets or other destinations.
So far it is still not clear why higher specific impulse is good  or how good it is.
Let me give you a practical example. Consider the famous rocket equation given below:
 M/m = exp( dv/g*Isp )
 where:
 M = initial total mass
 m = final total mass (after the fuel is used up)
 M/m = mass ratio
 exp =
"e" raised to the power of ( dv/g*Isp )
 dv = total delta velocity
 g = acceleration of gravity
 Isp = specific impulse of the fuel or the propulsion system
My plan calls for an outward velocity of 20 km/sec and the same for the return trip.
This amounts to a total delta velocity of 40 km/sec or 40,000 m/sec.
Let's calculate the mass ratio for a LOXLH2 rocket:
We have: M/m = exp(40000/9.8 * 450) = exp(9.07) = 8693
Now we do the same for a nuclear thermal rocket with an Isp of 950 secs.
We now have: M/m = exp(40000/9.8 * 950) = exp(4.296) = 73
Finally, try my system with an Isp of 3300 secs.
Now we get: M/m = exp(40000/9.8 * 3300) = exp(1.24) = 3.44
The results are summarized in the table below.
Comparison of Propulsion Systems for 3000 MT Spaceship
Propulsion system 
Isp 
Total Mass(MT) 
Total Cost at $1M/MT 
LOXLH2 (shuttle) 
450 
26,079,000 
$26,079,000,000,000 
Nuclear Thermal 
950 
219,000 
$219,000,000,000 
Momentum exchange 
3300 
10,320 
$10,320,000,000 
