Comparisons to other Systems

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2.3 Comparisons to other Systems

 

Antimatter can be used very efficiently in propulsion activities.  Proton-antiproton annihilation is a much better means of propulsion than that of anti-electron annihilation.  Proton-antiproton particles are charged and confined to a certain area magnetically to produce thrust.  Anti-electron annihilation is very inconsistent and inefficient compared to that of antimatter propulsion.  Anti-electron annihilation produces only high-energy gamma rays, which cannot produce thrust and would require the space vessel to be completely shielded [6]. 

Numerous propulsion systems exist where chemical propulsion is the most common and used in space exploration.  Chemical propulsion systems are beneficial because cost savings are existent through smaller launch vehicles.   However, small percentage changes in chemical propulsion can drastically change the vehicle size and cost.  Research of chemical propulsion can be hard to understand because the technology is complex.  Trajectory optimization is also very tough with chemical propulsion systems.  It is also hard to simplify the mechanical and thermodynamic cycles.  Ionizing a gas is another form of propulsion.  With this system, there are advantages and disadvantages to be considered.  First, for the advantages, there exist a wide range of thrust capability and the development cost is relatively small.  In addition, the specific impulse for an ion propulsion system has a wide range and there are a variety of propellants that are available.    Second, for the disadvantages, there is a lack of availability of power systems to meet thruster capabilities.  Furthermore, there also exists a political issue involving the use of nuclear power sources to power the ionization [12].  Nuclear fission and fusion can also be used as a propellant and are ideal for deep space exploration.  For fission, propulsion will reduce mission times and technical risks.  However, problems exist because nuclear reactors and shielding are heavy, which causes payload to be cut.  It is difficult to reduce the size and weight of the nuclear reactor for space applications [12].  Fusion propulsion systems give advantages on trip times.  The size of fusion systems can be a disadvantage because they are so big.  Antimatter propulsion systems could give smaller and lighter vehicles and the storage area is relatively small.  There is a small thrust to weight ratio and a high specific impulse in antimatter propulsion systems [12].  Table 1 below shows the specific impulse and the thrust-to-weight ratio of the various propulsion systems. 

Propulsion Type

Specific Impulse [sec]

Thrust-to-Weight Ratio

Chemical

200 - 410

.1 - 10

Ion

1200 - 5000

10-4 - 10-3

Nuclear Fission

500 - 3000

.01 - 10

Nuclear Fusion

10+4 - 10+5

10-5 - 10-2

Antimatter Annihilation

10+3 - 10+6

10-3 - 1

 Table 1. Propulsion Concepts [11]

 

Applications of Antimatter | Comparisons to other Systems | Consequences

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Last updated: 12/07/03.