NASA's space hot-rod

Exclusive: NASA's new space 'hot rod'


By Frank Sietzen
United Press International


Part 2 of 2


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Editor's Note: Planners in NASA's Exploration Directorate recently
gave United Press International an exclusive briefing on the steps
they envision to fulfill President Bush's new vision for space
exploration. These steps include designing the vehicle to fly back to
the moon as well as the new fleet of atomic-powered spacecraft that
may open up astronaut visits to deeper in space. In Part 2, NASA
attempts to develop a new nuclear rocket and power system that could
shrink the time it takes astronauts to travel through the solar system
-- as well as boost power for a whole new generation of space probes
and moon bases.

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WASHINGTON, July 30 (UPI) -- To send astronauts back to the moon, NASA
is planning to begin by making maximum use of existing U.S. and
foreign rockets as launching systems. Vehicles under consideration may
use updated propulsion systems that could blast a flotilla of
spacecraft from the Earth to the vicinity of the moon.

For voyages of longer duration, however -- to Mars and possibly even
more distant destinations -- NASA is designing a whole new system for
both space propulsion and space power. If successful, the system could
provide future astronauts a swifter means of voyaging far beyond the
moon and equip their ships and robotic scouts with far more electrical
power than ever has been available to space missions before.

Named for the Greek God that gave humans fire, Project Prometheus was
first announced in 2002, well prior to President Bush's space
exploration proposals.

Prometheus originally was conceived as a revamped package under NASA's
Nuclear Systems Initiative. It was intended to develop and
flight-demonstrate an advanced, atomic-powered space vehicle. The
vehicle, which NASA prefers not to call a rocket -- rather, a nuclear
electric propulsion system -- might be able to triple the speed at
which spacecraft travel beyond the Earth.

The heart of the Prometheus research effort -- a $3 billion project
planned across five years -- would be a set of power systems evolved
from the powerplants and electric thrusters carried aboard existing
space probes.

Instead of conventional rockets, which start out with a maximum thrust
of short duration, a nuclear-electric space vehicle would fly away
from Earth slowly, then gradually increase its speed via continuous,
long-lasting thrust from relatively small, electric engines.

NASA periodically has studied such engines for deep space use, but to
date has not developed or flown them as the main propulsion system for
probes or spacecraft. Their only use has been to control the orbital
position of Earth satellites.

Nevertheless, NASA planners seem excited by the potential of
Prometheus as a source of greatly increased power, and they are
studying two alternative power systems.

One would be an advanced version of the radioisotope thermoelectric
generators currently in use aboard probes such as the Cassini
spacecraft, which currently is orbiting Saturn.

Planners are exploring two RTG technologies: the Multi-Mission
Radioisotope Thermoelectric Generator, and the Stirling Radioisotope
Generator. Both would advance existing RTG technology into the 21st
century.

Cassini employs three such generators to produce electricity for the
probe's four-year mission around the Saturnian system, but the maximum
amount of power the trio can generate is only 30 volts, with an output
of about 870 watts.

The second technology is a nuclear fission reactor power system. The
technology, never outfitted on to U.S. spacecraft, could yield a
massive increase in a spacecraft's electric power. Planners liken such
an advance to the difference between a 100-watt electric light bulb
and a lighted baseball stadium.

Officially, all that NASA predicts is a spacecraft using a fission
reactor for its power would have 100 times more electricity as a probe
without it. That much power would allow scientists to carry much more
advanced instrumentation aboard the probes of the future.

"We asked the scientific community, 'what could you do if you didn't
have (today's) restrictions on power?,'" NASA Administrator Sean
O'Keefe told UPI. The answer was to build and fly space probes that
would be of an order of magnitude above today's craft.

Future space probes powered by NFRs could:

-- Perform exquisitely detailed detailed photo-reconnaissance of the
giant planets -- Jupiter, Saturn, Uranus and Neptune -- as well as
their many moons.

-- Rendezvous with comets in space, subjecting them to detailed
inspection and collecting samples to return to Earth.

-- Carried aboard a Mars lander, NFRs could increase by many times the
number of instruments set down on the surface, as well as the
complexity and capability of the mission, the distance traveled on the
surface and, possibly, allow the transport of a piece of the red
planet back to Earth.

-- Aboard deep-space robotic expeditions to the farthest edges of the
solar system, they would power investigations of Pluto, the Kuiper
Belt and perhaps even the mysterious Oort Cloud.

Using the solar power to provide electricity to spacecraft would not
work at such great distances. The power of sunlight at Saturn, for
example, is only 1 percent of its strength at Earth.

NASA already is planning deep-space missions that a Prometheus power
system might enable. Last spring, a team of researchers studying a
mission to the moons of Jupiter began the process of evaluating the
kinds of instruments they might want to place aboard the flight.

Called the Jupiter Icy Moons Orbiter, or JiMO, the spacecraft would
move in and out of orbit around three of Jupiter's moons -- Callisto,
Ganymede and Europa -- powered by the Prometheus reactor and its
electrical propulsion engines.

Using the electricity generated by the reactor, JiMO would be capable
of adjusting its orbit to aim its advanced, power-hungry cameras and
instruments at features it found interesting on the Jovian lunar
surfaces.

In addition to demonstrating the NFR concept, JiMO would attempt to
scout the moons for their ability to sustain life, map their surfaces
or penetrate sub-surface oceans with advanced space radar, and conduct
studies of the chemical composition of the surfaces or the depth and
make up of ice covering their liquid oceans.

JiMO also would study the radiation surrounding the moons, as well as
their magnetic fields.

Among the instruments being evaluated for the mission -- which would
not be launched before 2011 -- are new types of space radars,
magnetometers, infrared imagers and high-resolution cameras, as well
as new equipment to study the atoms and dust in space near each of the
planetary bodies.

Still, just getting JiMO aloft will be difficult for NASA.

"Prometheus will be a challenge," said Mike Lembeck, in charge of
requirements for NASA's Exploration System Directorate.

When completely deployed in space, JiMO and its Prometheus power and
propulsion system will be more than 100 feet long. Currently, Lembeck
said, there are no existing space boosters capable of lifting the JiMO
package into space as a complete unit -- NASA's preferred plan.

"So, we may have to launch in two or three pieces," Lembeck said. NASA
also might have to assemble JiMO robotically, he added.

Interest in a heavy-lift rocket may drive the booster choices for the
moon-Mars program, because the heavy-lifting space shuttle fleet is
scheduled to be retired by 2010.

If NASA opts for a big cargo booster for JiMO, it might also employ
the vehicle in the planned human assault on the moon and Mars.

The Prometheus reactor also is being eyed to power lunar and Martian
expeditions and bases, Lembeck said.

"The JiMO mission is a way to test out this technology" for later use
in the manned landings, he explained.

Thus, NASA's new, space-going hot rod will be getting its early
workouts powering new generations of robotic space probes, but it
ultimately will find its home with humans, providing light, heat and
power on other worlds.

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Frank Sietzen covers aerospace for UPI Science News. E-mail

I suppose with much more power, you could increase your bandwidth in
transmitting pictures back, implying you could have multiple cameras sending at
the same time, in real time, without always having to first store and compress
it. With sufficient juice, you then also have laser ranging and radar imaging
become possible.

In sci.space.policy Andi Kleen wrote:
(Steve Dufour) writes:
snip
Future space probes powered by NFRs could:

-- Perform exquisitely detailed detailed photo-reconnaissance of the
giant planets -- Jupiter, Saturn, Uranus and Neptune -- as well as
their many moons.

Perhaps I'm dense, but how does more power help with photo-reconnaisance?
I suppose today's CCDs are not really limited by available power.

Perhaps they want to add a flash light @)

I suppose a spacecraft with better propulsion could carry more
heavy optics, but is there any other advantage I'm missing?

If you've got delta-vee to burn, you can actually go to look at something,
rather than doing eighty-three gravity assists to reach it in only a
few years.

Cassini for example is a good example of this.
If it had lots and lots of fuel to burn, it could go into orbit round
each of the moons in turn, and do detailed orbital surveys.

In article ,
Andi Kleen wrote:
-- Perform exquisitely detailed detailed photo-reconnaissance of the
giant planets -- Jupiter, Saturn, Uranus and Neptune -- as well as
their many moons.

Perhaps I'm dense, but how does more power help with photo-reconnaisance?
I suppose today's CCDs are not really limited by available power.

There are minor limitations in transmitting the pictures back, but the
imaging systems themselves aren't power-intensive. They are *probably*
thinking of being able to orbit each moon rather than doing brief flybys.
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"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |