We commonly refer to the central "object" in extra-galactic radio sources as the "engine" that is the root cause of many radio source characteristics. We frequently ask, COULD "engines" at the cores of extra-galactic sources: (1) be compact objects with accretion disks; (2) eject well-collimated supersonic jets; (3) show relativistic effects in ejected material; (4) produce twin-jets; (5) produce one sided jets; and (6) initiate highly polarized synchrotron radiation sources? SS433 is a binary

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... tar system with radio and optical jets that is relevant because it is a "li ttle engine that could", and does, do all of these things. Further, we can observe changes in SS433 on time scales from hours to several months, and these data allow one to study evolution of jets in a more thorough fashion than is possible for extra-galactic sources. The SS433 star system (V1343 Aql) has optical emission lines (Margon et. al. 1980) which change wavelength in a manner corresponding to a doppler shift range of 80,000 km/s with a periodicity of 164 days. These emission lines of H I and He I have been interpreted (Margon et. al. 1980) in terms of recombining material in twin-jet flows that have a velocity of 0.26c (c = the speed of light), a jet axis either 80 degrees or 20 degrees to the line of sight, and an ejection vector that rotates around the jet axis every 164 days at an angle of 20 degrees or 80 degrees. SS433 was independently found to be a radio source by Ryle et. al. (1979) and Seaquist et. al. (1979), and as can be seen from the large scale map of Geldzahler et. al. (1980), is a compact radio source inside the 1 degree by 2 degree "supernova remnant" W50. Johnston et. al. (1981) have shown that the relatively steady radio emission from SS433 is combined with flaring events that increase the flux density of the source by up to a factor of two with event time scales of 1-5 days. The radio emission is synchrotron emission from highly relativistic electrons because of the omnipresent non-thermal spectral index of 0.6 and the observation of linear polarization of up to 20% in the jets (Johnston et. al. 1981 and Hjellming and Johnston 1981a). The SS433 radio source was first found to have structure on angular scales of 0.1"-5" by Gilmore and Seaquist (1980). SS433 also shows structures on 197 D. S. Heeschen and C. M. Wade (eds.J, Extragalactic Radio Sources, 197-204.