Orion

Why would NASA promote a human space expedition to Mars when drone programs prove so successful? And to the stars, wait a minute.

Even if the crew survives, the uncontrollable cosmic radiation seriously damages both the vascular and neurological systems. Even though astronauts return younger in relation to those they left behind, the damage is not repairable. How much better to launch a drone, robotic in every respect, with the astronaught sitting comfortably and safely behind an earthbound flight deck, nine to five, evenings and weekends at home, thus solving the human factor issue and providing easier and better engineering of the space vehicle. Without the fragile and demanding attention to a survivable habitat, there would be far less space, energy and weight demand, leaving room to perfect the mechanics of the mission, mechanics that could do more than what is humanly possible. 

No longer requiring human scale, the whole project could be miniaturized, further improving the power to weight demand, never mind cost. Robotics should be the future -- a vast improvement on space probe launches in the past.

Time lag, like a satillite phone, becomes a problem with remote control. By the time a signal arrives for a maneuver, it may already be too late. Two solutions: one artificial Inteligence, and two, quantum computing, both of which are advancing rapidly. Is it science fiction to envision quantum entanglement as a means of realtime control of a drone at great distance and to what limit? -- to the stars? Artificial Inteligence seems more likely. The earthbound astronaught might discuss strategy with an onboard artificial Inteligence, 2001 without the onboard passenger or a holograph if you must, an avatar. Nanoscale might even become feasible; someone already proposed tiny space sail capsules.