Next Floor: The Moon
SpaceScience.com; Sept. 7, 2000; NASA Science News: "Audacious & Outrageous: Space Elevators"
"One of the fundamental problems we face
right now is that it's so unbelievably expensive to get things into orbit,"
says Jerome Pearson. "The space elevator may be the answer." The
concept of a "Space Elevator" may sound to you like something out of a
science fiction story -- and you'd be right. After Pearson's 1975
technical paper on the subject was published, it served as inspiration for
the elevator described in Arthur C.
Clarke's (1978) Fountains
of Paradise sci-fi novel.
The 1999 space infrastructure conference at NASA's Marshall Space Flight Center, that Pearson participated in, took a fresh look at designing this structure and what technology developments would be required to make it a reality. The findings are summarized in publication form: "Space Elevators: An Advanced Earth-Space Infrastructure for the New Millennium."
As envisioned by the conference, a 30-mile high tower would be built at an equatorial site on Earth. Cables, similar in strength to carbon nanotubes (100x stronger than steel), would extend from the top of the tower to geostationary orbit (35,786-km) and beyond. A large mass at the space end of the cable is needed to counterbalance it and bring the center of mass of the system to the geostationary point. This keeps the cable steady over the equatorial tower. Magnetic levitation vehicles would be propelled along the cable at thousands of kilometers-per-hour. The final result would greatly reduce the price of space access from $10,000 per pound (Space Shuttle) to the astounding cost of just a few dollars!Five major technological developments were highlighted that would make the elevator feasible. First is the construction of cables from carbon nanotubes. These tubes, with diameters in nanometers, have a strength similar to diamond, but not the brittleness. Second is continuation of the technical development and experience with tether technology in space. Next is lightweight structural materials for development of the towers. Forth was mag-lev technology for the "cable-cars" and fifth was the development of an infrastructure to support construction and industrial development in space.
The author of the publication envisioned that the above technologies would mature and enable construction of the elevator toward the end of the 21st Century.
Daddy, Where Do Meteorites Come From?
Space.com; Aug 5, 2000; News: "Project Hera: Triple-header Asteroid Probe"
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Asteroid composition ranges from iron objects, volcanic-like rock, and loose clumps of gravel. The various types of meteorites recovered around the Earth are believed to originate from the several classes of asteroids in our solar system. But there is no firm link between the asteroid and meteorite varieties because no asteroid material samples have ever been taken. Now a proposed $240 million " cheaper, better, and faster" NASA mission proposes to rendezvous with three asteroids to do such a sampling.
The samples returned by the "Hera" spacecraft would not only help scientists associate the meteorites with asteroid types, but determine conditions at solar system formation, give a clue as to what sort of impact such objects would make on the Earth, and establish what would be needed to deflect an errant one from striking our planet. Hera is designed upon the technological base and experience gained from several current missions. These include the NEAR probe in orbit around asteroid Eros, the Stardust spacecraft en route to return a sample of comet dust, and Deep Space 1's revolutionary ion engines and autonomous navigation software.
Hera is designed to float within feet of an asteroid body and extend a 1.5 meter boom tipped with counter-rotating drill bits to the surface. The asteroid drilling fragments are captured and transferred to sample-return canisters.
Drill depths are expected up to 1-meter below the surface. While still on the drawing boardb scientists have selected three tentative targets for Hera, all about 150 million miles from Earth.
The mission is currently scheduled for a January 2006 launch, with arrival at asteroid 1999 AO 10 in seven months time. After 99 days of surveying and acquiring samples from various parts of asteroid the craft will depart for asteroid 2000 AG 6. Arrival at that target will be in November 2008 with a 98 day stay. Afterwards it's onto asteroid 1989 UQ for a 205 day stay starting in March 2009. At the end of that period the craft will come back to Earth to parachute- return the samples in November 2010.
It's a Bird, It's a Plane? No! It's an SPS!
SpaceRef.com; Sept 7, 2000; News: "Congress Gets an Update on Solar Power Satellites"
"We don't need any breakthroughs. We need to apply what we already have here on the ground," is what Ralph Nansen told the House Science Committee's Subcommittee on Space and Aeronautics at a hearing last week. Nansen, President of Solar Space Industries, was there to discuss Solar Power Satellites (SPS) -- a technology with a history that dates to the Apollo Moon-landing era. As originally conceived, the system would put kilometer sized solar panels in geostationary orbit and beam solar energy to Earth, in the form of microwaves, for ground stations to distribute into the power grid as electricity. The idea got great attention during the oil crunches of the 1970s, but work on SPS was dropped in 1980 after a Department of Energy study pegged the cost of setting up such a system at $275 billion.
The purpose of the hearing was to measure technological progress made since a 1997 "Fresh Look" study by NASA concluded that advancements had made SPS more feasible. These include higher efficiency photovoltaic cells and improvements in transmitting energy via microwave and laser beams. Lasers transmission has gotten attention because it would suffer less dispersion through the atmosphere and require a smaller receiving antenna on the ground. It was noted that SPS technology could be used to "beam" a solar-sail spacecraft into the deep reaches of space. A further use of this technology could be for relaying energy transmitted up from Earth to another part of the planet. Subcommittee chair Rep. Rohrabacher voiced the opinion that more resources be put into developing the requisite technology. He noted that one of the technologies key to making the SPS concept viable is cheaper access to space.
At the end of the proceedings Rohrabacher said "we spent billions of dollars on fusion research - perhaps as much as $20 billion - and we don't have anything to show for that. People often call this 'white coat welfare'. You have to ask why we should be doing this. I don't think we should be spending money just to advance knowledge. Projects such as SPS can lead to the bettering of people's condition on this planet. I think that some of the money that was spent on fusion could have been spent on SPS and that it could have yielded clean energy from space by now had we done so. "
Don't Drink this Water
SpaceDaily.com;
Sept 14, 2000; Space Science: "Centaur's Bright Surface Spot
Could be Crater of Fresh Ice"
Between the orbits of
Neptune and Jupiter exits the region of space inhabited by the
Centaurs. Not the half-human and half-horse creatures from
mythology, but small bodies that resemble spent comet nuclei. The 21
known Centaurs are thought to have been cast out of the Kuiper Belt comet reservoir
beyond Pluto. Recently the Hubble Space Telescope studied 8405
Asbolus, a 48-mile-wide Centaur between Saturn and Uranus, with its Near
Infrared Camera and Multi-Object Spectrograph. Observations, separated
by hours, indicated that the object has two distinct faces.
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Artist conception. |
One side revealed a relatively bright, and complicated absorption spectrum while the other side of the object had a very smooth spectrum with few absorption lines. Scientists interpreted the results as meaning that one side had a "fresh" impact crater less than 10 million years old that exposed subsurface water ice and other compounds. Crater age is based on the knowledge that objects in the solar system darken and redden with exposure to ultraviolet sunlight, solar wind and cosmic rays.
While the spectrum of the bright hemisphere bears a strong resemblance to water ice, the match is not exact. "To wildly speculate, there may have been an impact that heated this surface and did some different chemistry of the hydrocarbons present. This may be a solar system ice that hasn't yet been seen in other objects or generated in the lab," says Donald McCarthy of the University of Arizona. "Perhaps the event that caused the impact crater on 8405 Asbolus also knocked it out of the Kuiper belt," McCarthy speculates.