The uranium will explode only after the spaceship moves away from Earth
Avi Blizovsky
On the left Jimmo will require more power than any previous spacecraft; Right: An artistic idea for the depiction of the Galileo spacecraft crash on Jupiter
Update: see below: the uranium will explode only after the spaceship moves away from Earth
Start with the initial design of a nuclear spacecraft that will explore the moons of Jupiter
Avi Blizovsky
11/12/2003
Scientists have begun to plan in detail the proposal to build the next spacecraft to Jupiter's moons that may have life or at least life-supporting conditions on them - Europa, Callisto and Ganymede. The giant spacecraft that will visit each moon in turn and explore the subsurface oceans will require nuclear power and this may cause controversy.
NASA recently issued a call for the conceptual design of a spacecraft that would attack the icy moons of Jupiter. The plan and the mission were described at the annual meeting of the American Geophysical Society currently meeting in San Francisco.
The Galileo mission that ended earlier this year provided tantalizing clues that Europa Ganymede and Callisto may harbor oceans of liquid water beneath the surface made of frozen ice. "Where there is water, there can also be life, and the exploration of these places is the main motivation behind the proposed Jupiter Icy Moons Orbiter (Jimo).
Ronald Greeley of Arizona State University and Louise Procter of Johns Hopkins University jointly head the committee of scientists assigned by NASA to work on some of the mission's specifications. "Our initial team will examine whether there is liquid water under the ice sheet. The second concern is whether the chemistry there is suitable for life. We will be able to examine the composition of the ice. Then, our third concern will be to check what the source of energy is, since life needs energy.
One of the unusual requirements for the spacecraft is that it can jump from moon to moon. This, NASA says, will require much more energy than any other mission to date, and the only possible available source of energy is a nuclear reactor (such as the one found in nuclear submarines), which will provide electric propulsion for the spacecraft. This will also make it possible to use devices that are not normally placed on spacecraft because they consume too much energy. By comparison, the Cassini spacecraft currently on its way to Saturn includes a small plutonium unit, which provides 900 watts for the entire suite of instruments on the spacecraft. Jimo, on the other hand, will require kilowatts of power for each and every device.
However, when the memories of the space shuttle Columbia disasters are still fresh in the minds of the Americans and in light of the public debate that took place around the repeated passage of Cassini near the Earth designed to give it speed on its way to its destination, it is still not clear how the idea of placing a nuclear reactor on the end of a missile will be received by the public.
There are also other significant obstacles that must be overcome before Jimo becomes a reality - one of them is funding. But even if permission is received to continue the project, the mission will provide scientific data from space at a rate never seen before, and may answer one of the great questions of the universe - is there life outside of Earth.
According to Louise Procter of Johns Hopkins University, Greeley's partner in managing the team, "there will be more science on this spacecraft than on all the missions to Mars combined and the scientific output is expected to be no less small."
If funding is found for the mission, it will be launched in 2012 or later.
The uranium will explode only after the spaceship moves away from Earth
23/12/03
By Kenneth Chang New York Times
NASA is already working on a spacecraft for Jupiter, which will use nuclear energy
Illustration of the future spacecraft Jimo. You will be able to move from one Jupiter moon to another
Illustration: NASA
The nuclear energy industry may actually recover in space, on the way to the planet Jupiter. The development of nuclear energy has been faltering for decades due to the high costs, the fear of an accident like the one that happened in Chernobyl and the difficulty of disposing of radioactive waste. But NASA and planetary science experts see this energy source as an opportunity to open a new era in space exploration.
Nuclear energy is particularly useful for studying remote areas in space - a field of research that requires a rich source of energy, which was not available until now. "This is an unprecedented opportunity for research," said Dr. Ronald Greeley, professor of geology at Arizona State University.
Greeley co-leads a team of 38 scientists that has been working with NASA since February to define which science projects are suitable for a nuclear-powered spacecraft to enter Jupiter.
The proposed spacecraft, the Icy Moons Orbiter Jupiter ("the icy moons of Jupiter") or Jimo for short, will be able to carry modern equipment and have more power than previous spacecraft, and will be able to enter and exit the coffee orbits around the various moons of Jupiter. The team of scientists presented their recommendations at a conference of the American Geophysical Union, held in San Francisco earlier this month. Jimo, which is still in the planning stages, will cost several billion dollars. These will be invested, among other things, in the development of a nuclear reactor suitable for space flight. The earliest estimated launch date is 2011.
Jimo will have to address concerns about the possible consequences of a spacecraft accident. Up to 10% of spacecraft launches fail, and in Jimo's case there is a danger that a nuclear warhead will explode high in the atmosphere and scatter radioactive material. "The more you increase the use of nuclear energy in space missions, the more you increase the risks," said Bruce Gagnon, coordinator of an organization called "The Global Network Against Nuclear Weapons and Power in Outer Space."
Launching a spacecraft such as Jimo would also be a "breakthrough for institutionalizing the use of nuclear power in space," Gagnon said. According to him, this power "will later be used for military needs", such as activating laser beams from space. NASA sources said that the nuclear reactor will not be activated until after the spacecraft reaches its orbit, and that safety will be at the forefront of the spacecraft's designers. The nuclear fuel will be processed so that it will not break up even if the spacecraft explodes.
NASA is tempted to use a small nuclear reactor for propulsion in space, because the energy becomes really expensive as you move away from the sun. At the edge of the solar system, sunlight is too weak to use solar panels and technologies such as fuel cells are not reliable enough when it comes to the journey to distant planets, which could take years. So far, NASA has used radioactive plutonium blocks, which produce heat when they decay; This heat is converted to electricity in modest amounts.
NASA's Galileo spacecraft, which in September completed a highly successful mission that lasted 14 years and ended in a deliberate collision with Jupiter, existed on electricity doses of several hundred watts - an amount consumed by a few light bulbs. This was enough for Galileo to make many discoveries, especially about Europa, one of Jupiter's moons. Cameras recorded Europa's cracked ice sheet and measurements of the magnetic field testified that beneath the ice there is a layer of electrically conductive material. Planetary science experts believe it is a liquid ocean, and it may be the most likely place to find life in the solar system.
Galileo, however, could not enter orbit around Jupiter's moons, and on its short flights near Europa only high-resolution images of 0.1% of the surface were taken. In contrast, nuclear propulsion would allow Jimo to be put into orbit around one moon for a few months, then relaunched to launch the spacecraft to the next destination.
The nuclear reactor placed in the spaceship will provide it with energy a thousand times greater than what has been available for missions in space so far. This would allow energy-hungry instruments, such as ground-penetrating radar, to check what lies beneath the surface of the planets. One of the scientists' ambitions is to study the geological history of the surface on the moons of Jupiter and to identify the types of molecules found there, especially those that suggest the existence of living beings.
The idea of nuclear propulsion is not new. In the 50s, the United States tried to develop a missile powered by small atomic bombs. The new initiative is much less dramatic. A uranium fission reactor that will be placed in the spaceship will generate heat. The heat will be converted into electricity, which will operate an ion thruster - an engine that uses electric fields to accelerate ions to very high speeds, which generates motive power.
NASA conducted a successful experiment with ion engines in the "Deep Space" experimental spacecraft in 1998. The ion engines on the Jimo will be at least 10 times more powerful. NASA's Glenn Research Center announced last month that an experiment on a possible model of the engine was crowned with success.
