It is a generally accepted fact that construction of a high-power proton accelerator (HPPA) capable of driving a system of nuclear subcritical assembly for nuclear transmutation or energy amplification is feasible theoretically and conceptually. However, there are a number of technological challenges in several areas that need to be solved so ADS can become feasible. In this paper, we discuss the key requirements of ADS, available technologies and extension and/or extrapolation of today’s technology to render the ADS practical. ADS technology would necessarily be an extension of the accelerator of the Spallation Neutron Source (SNS), which is under construction at Oak Ridge National Laboratory. A discussion on how to extend SNS technology to ADS technology is also provided. As both accelerator and target/reactor would operate in uncharted regions of performances, extending and integrating today’s technology to the ADS realm would require many performance/requirements trade-offs between accelerator and reactor designers. The uncharted regime of performance includes two to three orders of magnitude higher beam power, improving the reliability of the accelerator to that of a similar range of reactor, and improving and controlling accelerator beam loss fraction to the 10–6 range in order to facilitate hands-on maintenance of the accelerator system. An opinion on a possible road map to achieve the ADS goals is also provided.