I believe as a matter of faith that the extension of space travel to the limits of the solar system will probably be accomplished in several decades, perhaps before the end of the century. Pluto is 4000 million miles from the sun. The required minimum launching velocity is about 10 miles per second and the transit time is 46 years. Thus we would have to make the velocity considerably higher to make the trip interesting to man. Travel to the stars is dependent on radically new discoveries in science and technology. The nearest star is 25 million million miles way and requires a travel time of more than four years at the speed of light. Prof. Dr. Ing. E. Sanger has speculated that velocities comparable with the speed of light might be attained in the next century, but such extrapolation of current technology is probably not very reliable.

I think we need someone in a responsible political position to have the courage to say, 'Let's terminate human spaceflight.'
As a staunch advocate of robotic missions.

I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

In a dispassionate comparison of the relative values of human and robotic spaceflight, the only surviving motivation for continuing human spaceflight is the ideology of adventure. But only a tiny number of Earth's six billion inhabitants are direct participants. For the rest of us, the adventure is vicarious and akin to that of watching a science fiction movie. At the end of the day, I ask myself whether the huge national commitment of technical talent to human spaceflight and the ever-present potential for the loss of precious human life are really justifiable.

In the infancy of physical science, it was hoped that some discovery might be made that would enable us to emancipate ourselves from the bondage of gravity, and, at least, pay a visit to our neighbour the moon. The poor attempts of the aeronaut have shewn the hopelessness of the enterprise. The success of his achievement depends on the buoyant power of the atmosphere, but the atmosphere extends only a few miles above the earth, and its action cannot reach beyond its own limits. The only machine, independent of the atmosphere, we can conceive of, would be one on the principle of the rocket. The rocket rises in the air, not from the resistance offered by the atmosphere to its fiery stream, but from the internal reaction. The velocity would, indeed, be greater in a vacuum than in the atmosphere, and could we dispense with the comfort of breathing air, we might, with such a machine, transcend the boundaries of our globe, and visit other orbs.

It [space travel] will free man from his remaining chains, the chains of gravity which still tie him to this planet. It will open to him the gates of heaven.

Mankind will not remain on the earth forever, but, in search of light and space, will at first timidly penetrate beyond the limits of the atmosphere and then finally conquer the spaces of the solar system.

My position is that it is high time for a calm debate on more fundamental questions. Does human spaceflight continue to serve a compelling cultural purpose and/or our national interest? Or does human spaceflight simply have a life of its own, without a realistic objective that is remotely commensurate with its costs? Or, indeed, is human spaceflight now obsolete?

The world we know at present is in no fit state to take over the dreariest little meteor ... If we have the courage and patience, the energy and skill, to take us voyaging to other planets, then let us use some of these to tidy up and civilize this earth. One world at a time, please.