CURIUM-244 ALPHA-EMISSION FOR A NANO-NEWTON AND MICRO-NEWTON THRUSTER

We have recently suggested [1] to exploit particles emitted by nuclear reactions as a thrust source for applications to satellites. The main advantages are very high specific impulse and simplicity of the appar atus; the drawback is the low total thrust obtainable even for high ac tivity of radio nuclides. This simple idea has raised some interest an d a paper [2] has been published where our calculations are improved ( we thank tile author for corrections and discussions) confirming the r obust validity of tile idea. In [2] the method is applied to deep spac e propulsion bypassing the low thrust problem increasing the activated surface and using a ''radioisotope sail''. Furthermore [2] contains a bibliography going back to a 1961 textbook that contains discussions before 1940. The idea, being very simple, has been probably explored s ince the very beginning of the nuclear era. However the thrust for a s quare meter of radioactive isotope is such a low number (10 mu N/m(2)) that it easy to understand why this simple method was discovered and immediately discarded and neglected. What has changed in the last 50 y ears is not our knowledge of nuclear reactions but the interest for a new technological target; today it is important to deal with very low and very precise thrust to improve the attitude and control system of satellites. In particular the method proposed ensures a good tunabilit y in the region between the nanoNewton and the microNewton, at varianc e with other more conventional methods, with minimal weight and size ( of order of 0.1 m(2)). This idea, discarded because not suitable for h igh thrust, has been rediscovered and could be very useful for the fin e tuning of very low thrusts.