[geocentrism] space power supply
- From: "philip madsen" <pma15027@xxxxxxxxxxxxxx>
- To: "geocentrism list" <geocentrism@xxxxxxxxxxxxx>
- Date: Sun, 8 Apr 2007 13:49:50 +1000
http://zmagsite.zmag.org/Apr2003/grossman0403.html
was very interesting , and here is a selected portion from another site. Phil
2. Technology
2.1 The U.S. - RTG, Nuclear Reactor, And RHU
2.1.1 Radioisotope Thermoelectric Generators (RTGs)
2.1.2 Nuclear Reactors
2.1.3 Radioisotope Heater Units (RHUs)
2.2 The USSR/Russia - RORSAT, Topaz, And RTG
2.2.1 RORSAT Nuclear Reactors
2.2.2 TOPAZ
2.2.3 Radioisotope Thermoelectric Generators (RTGs)
2.2.4 Radioisotope Heater Units (RHUs)
2.3 Other Nations - "RTG Technology Is Not Available"
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2.1 The U.S. - RTG, Nuclear Reactor, And RHU
2.1.1 Radioisotope Thermoelectric Generators (RTGs)
All but one of the nuclear powered space missions launched by the U.S. used
RTGs. In a document about the Ulysses mission, ESA/ESTEC (European Space
Agency/European Space Research and Technology Center) explains the RTG
technology as follows:
"What Are RTGs?
RTGs are lightweight, compact spacecraft power systems that are highly
reliable. RTGs are not nuclear reactors and have no moving parts. They use
neither fission nor fusion processes to produce energy. Instead, they provide
power through the natural radioactive decay of plutonium (mostly Pu-238, a
non-weaponsgrade isotope). The heat generated by this natural process is
changed into electricity by solid-state thermoelectric converters. RTGs enable
spacecraft to operate at significant distances from the Sun or in other areas
where solar power systems would not be feasible. In this context, they remain
unmatched for power output, reliability and durability.
Safety Design
More than 30 years have been invested in the engineering, safety analysis and
testing of RTGs. Safety features are incorporated into the RTG's design, and
extensive testing has demonstrated that they can withstand physical conditions
more severe than those expected from most accidents.
First, the fuel is in the heat-resistant, ceramic form of plutonium dioxide,
which reduces its chance of vaporizing in fire or reentry environments. This
ceramic-form fuel is also highly insoluble, has a low chemical reactivity, and
primarily fractures into large, non-respirable particles and chunks. These
characteristics help to mitigate the potential health effects from accidents
involving the release of this fuel.
Second, the fuel is divided among 18 small, independent modular units, each
with its own heat shield and impact shell. This design reduces the chances of
fuel release in an accident because all modules would not be equally impacted
in an accident.
Third, multiple layers of protective materials, including iridium capsules and
high-strength graphite blocks, are used to protect the fuel and prevent its
accidental release. Iridium is a metal that has a very high melting point and
is strong, corrosion resistant and chemically compatible with plutonium
dioxide. These characteristics make iridium useful for protecting and
containing each fuel pellet. Graphite is used because it is lightweight and
highly heat-resistant." [ESTEC/b]4
On its web page "Cassini RTG Information", NASA's Jet Propulsion Laboratory
gives additional technical information:
"Each RTG NASA uses on recent planetary spacecraft contains approximately 10.9
kg (24 lb.) of plutonium dioxide fuel. On Galileo's two RTGs, that amounted to
a total of about 48 lb. On Cassini, which has three RTGs, it's about 72 lb. ...
RTGs have been used on 23 U.S. space missions including Voyager, Pioneer,
Viking, Apollo, and more recently the Galileo and Ulysses missions5. As in the
past, Cassini's RTGs are to be provided by the U.S. Department of Energy (DoE).
Heat source technology pursued by DoE has resulted in several models of an RTG
power system, evolving from the Systems for Nuclear Auxiliary Power (SNAP)-RTG
to the Multi-Hundred Watt (MHW)-RTG, to the currently used General Purpose Heat
Source (GPHS)-RTG used on Galileo, Ulysses and Cassini spacecraft. The GPHS
technology is the culmination of almost 25 years of design evolution.
A GPHS-RTG assembly weighs 56 kg (123.5 lb), is approximately 113 cm (44.5 in)
long and 43 cm (16.8 in) in diameter and contains 10.9 kg (24 lb) of plutonium
dioxide fuel. At launch, the three RTGs will provide a total of 888 watts of
electrical power from 13,182 watts of heat. By the end of the mission the power
output will be 628 watts." [JPL/c]
A specific aspect of RTG usage is pointed out by Canadian journalist Michael
Bein: "Although the American planners have obviously been concerned enough
about safety to draft general criteria and institute a three-step, multi-agency
review process that must be completed before each launch, there are a number of
weaknesses in the U.S. regulatory system vis a vis NPS [Nuclear Powered
Satellites]. First of all, there is no licensing by an independent authority
like the Nuclear Regulatory Commission, the watchdog of America's commercial
nuclear power industry. All the nuclear missions flown to date have been
classed as research devices and have therefore been exempted from licensing
under a provision of the Atomic Energy Act. DoE, meanwhile, reserves the right
to approve deviations from the published safety criteria. And, perhaps most
importantly, there is no provision for public participation in the safety
review process." [BEIN]
2.1.2 Nuclear Reactors
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