25. September 2005 · Comments Off on The Word From On High · Categories: Science!, Technology

None other than Arthur C. Clarke himself chimes in on NASA’s further plans for space:

In 1969, the giant multistage rocket, discarded piecemeal after a single mission, was the only way of doing the job. That the job should be done was a political decision, made by a handful of men. (I have only recently learnt that Wernher von Braun used my The Exploration of Space (1952) to convince President Kennedy that it was possible to go to the Moon.) As William Sims Bainbridge pointed out, space travel is a technological mutation that should not really have arrived until the 21st century. But thanks to the ambition and genius of von Braun and Sergei Korolev, and their influence upon individuals as disparate as Kennedy and Khrushchev, the Moon — like the South Pole — was reached half a century ahead of time.

If Nasa resumes lunar missions by 2018, that timing would be just about right: it will be only a year short of the 50th anniversary of Neil Armstrong’s famous “one small step”. But banking on solid rocket boosters to escape from Earth, as being planned, will not represent a big technological advance over the Apollo missions. Even if the spacecraft are reusable, it will still cost hundreds of thousands of dollars to launch every kilogram into space. I think the rocket has as much future in space as dog sleds in serious Antarctic exploration. Of course, it is the only thing we have at the moment, so we must make the best use of it.

But I would urge Nasa to keep investing at least a small proportion of its substantial budget in supporting the research and development of alternatives to rockets. There is at least one idea that may ultimately make space transport cheap and affordable to ordinary people: the space elevator.

First conceived by a Russian engineer, Yuri Artsutanov, in 1960, it was reinvented by a group of American scientists a decade later. And it’s based on a simple — yet daring — concept.

Today’s communications satellites demonstrate how an object can remain poised over a fixed spot on the Equator by matching its speed to the turning Earth, 22,300 miles (35,780 km) below. Now imagine a cable linking the satellite to the ground. Payloads could be hoisted up it by purely mechanical means, reaching orbit without any use of rocket power. The cost of launching payloads into orbit could be reduced to a tiny fraction of today’s costs.

I differ with the great author on two points: First, it was by no great vision or effort of von Braun or Korolev that we reached the Moon in 1969, rather than 2019, but the quest for military superiority. Not to deny their genius. But, had they never even existed, the achievement – or something of similar technological magnitude – would have occurred no more than a decade, rather than a half-century, later.

Second, orbit in the Clarke Belt is achieved because the centrifugal force of the orbiting satellite exactly matches the force imparted upon it by gravity. Propelling a payload up a tether attached to that satellite would upset that equilibrium. Further, their is the distributed mass of the tether itself to consider. It is therefore necessary that the satellite be in a far lower orbit, in order to maintain tension on the tether. Indeed, the path the transport vehicle takes to reach the satellite will not be a straight path, as is popularly envisioned, but a great parabolic arc.

Read the whole thing.

Hat Tip: InstaPundit

Update: A bit red-faced after that sign-inversion. But those sort of things happen when you’re bouncing these things around in your head.

In any event, I never said the space elevator wouldn’t work, only that it wouldn’t be quite as currently envisioned. I still feel that the cable will arc into space, And it appears this effect has already been contemplated for the mass of the transport vehicle (“climber”, if you will), but not for the distributed mass of the cable itself.

Update: There is a spirited debate (of which I am pretty much on the defensive) on this subject, over at Transterrestrial Musings.

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