Friday, June 24, 2011
Don't worry, that's just the international space station. It isnt "our"
space station of course; its operation is overseen by five separate space
agencies. Nevertheless we bear a major responsibility for this $160
billion monument to the age of manned space flight. Left alone, its a
417,000 kg missile that will return to Earth traveling at 28,000 km/h. I
leave it to the students to calculate the energy. I raised this point in
1998 when ISS assembly began and was told it would be disassembled and the
parts returned to Earth on the shuttle. President Obama might prefer to see
this done with commercial space vehicles, except they don't exist yet.
Controlled or uncontrolled, the ISS will return to Earth.
The space race with the Soviet Union ended with Apollo-17. Both countries
explored the Moon, brought back piles of moon rocks, and took astounding
photographs, but today few even remember that the USSR had a Moon program.
They had chosen to do it with robots; more technologically advanced than
Apollo perhaps, but it counted for little in the hearts and minds of the
public. You can't give robots tickertape parades down Broadway. Apollo was
followed by the Space Shuttle. For a time, every space mission had to
begin with a shuttle launch, guaranteeing a constant supply of heroes but
the shuttle could not keep up with the demand for launches. Atlantis is
now being prepared for a July 8 launch. A prosaic 12-day "UPS" flight to
deliver supplies and equipment to the International Space Station, it will
be the final mission in the 30-year-old shuttle program. Sold to Congress
as a cost-effective way to get into space, the shuttle will be remembered
as the most expensive launch system ever devised.
This, of course, is the NASA that does science. A new species of NASA rover
has evolved named "Curiosity." It will resume exploration of the Martian
surface begun by little Sojourner, which landed on Mars on July 4, 1997.
The new rover is bigger and faster with far more sophisticated laboratory
than previous rovers. Yesterday's issue of Nature identifies the Gale
Crater, a 150-kilometre wide depression, as the destination preferred by
mission scientists. The decision will be made, perhaps today, by associate
administrator Ed Weiler.
Curiosity will be powered by the heat given off by the natural decay of Pu-
238, a non-fissile isotope of plutonium with a half-life of 87.7 years. An
alpha emitter, it is easily shielded. Pu-238 RTGs are essential to a number
of spacecraft missions, particularly those bound for the outer solar
system. United States currently has limited facilities to produce Pu-238.
Since 1993, all of the Pu-238 the U.S. has used in space probes has been
purchased from Russia. 16.5 kilograms in total have been purchased. The US
Department of Energy is requesting funding to restart domestic production,
but production of substantial amounts could take 5 years.
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