Electric: If we assume a vehicle cost of a billion dollars, Fof$1000, and ignoring tm and vm we get Chemical: P = $2.9* 107 Nuclear: P = $2.5*107 Electric: P = $8.4* 107 We find that when the vehicle requires large mission times that the cost of the vehicle can have a significant impact on the break-even price. This is a fact that much work has ignored. So far, a great deal of work has concentrated on specific impulses of rocket engines to be used in the transfer, in order to minimize the fuel requirements of the mission. For this reason, a lot of attention has been paid to electric propulsion. It is easy to achieve high specific impulses with these systems. However, electric propulsion systems have very poor thrust to mass ratios. Because of its poor thrust to mass ratio (using the formula we developed for the break-even price of a vehicle), we found that electric propulsion compared unfavorably to either chemical or nuclear propulsion. The poor thrust to mass ratio of electric propulsion leads to large transfer times. These large transfer times then increase the break-even price for the vehicle by increasing the fixed cost that must be assigned to each mission. We have found that at the Au’s we are considering that the critical performance parameter is the thrust to mass ratio. Future work on these systems should therefore concentrate on this factor rather than the exhaust velocities. Since the viability of any new space system will be based on its economic advantages, concentration on a very narrow technical figure of merit does not always allow the best comparison of systems of differing technologies. The method used here of looking at system performance in terms of the economics of the system is a useful one and deserves more attention. BIBLIOGRAPHY H.R. Kaufman and R.S. Robinson, Electric Thruster Performance for Orbit Raising and Manuevering, J Spacecraft Rockets, 21, pp. 180-186, 1984. R.M. Jones, Comparison of Potential Electric Propulsion Systems for Orbit Transfer, J Spacecraft Rockets, 21, pp. 88-95, 1984. R.A. Willaume, A. Jaumotte, and R.W. Bussard, Nuclear, Thermal and Electric Propulsion Fundamentals, Systems, and Applications, Gordon and Breach, New York, 1967. R.A. and P.B. Musgrave, Public Finance in Theory and Practice, McGraw-Hill, New York, 1980.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==