From: GBurch1@aol.com
Date: Sun Aug 15 1999 - 07:48:14 MDT
In increasing order of "mad-scientist factor", here's three interesting
pieces about promising new propulsion technologies (apologies if these have
appeared here before; I've been weeding pretty ruthlessly in my in-box and
may have missed a previous post of these items):
* * *
Sacramento - August 10, 1999 - NASA's Marshall Space Flight Center (MSFC) has
awarded GenCorp Aerojet a multimillion dollar extension for continued
development of the Strutjet Rocket-Based Combined Cycle (RBCC) engine through
2001.
This revolutionary propulsion system combines air-breathing and rocket engine
technologies in a single engine for use on future reusable,
single-stage-to-orbit launch vehicles. This type of engine allows the vehicle
to take off horizontally, like an airplane, for greater safety and
reliability and a dramatic reduction in cost of access to space. The Strutjet
RBCC is a candidate as the primary propulsion for a third-generation space
shuttle engine.
"Aerojet is proud to be working closely with MSFC as it moves forward on
reusable launch vehicle technology. We believe our technology will provide
the capability for early demonstration of a vehicle powered by an RBCC
engine," said Bob Harris, vice president, Strategic and Space Propulsion.
Since 1996, Aerojet has successfully progressed in building the Strutjet
RBCC, which is part of MSFC's Advanced Reusable Technologies Project. This
contract extension will refine the Strutjet RBCC into a highly integrated
engine/vehicle concept, and a new emphasis will be placed on the development
of flight-type cooled components, including the use of advanced materials and
fabrication processes. These flight-type components will be exposed to engine
thermal environments in a Component Development Rig at Aerojet's Sacramento
site.
The Strutjet RBCC is an advanced, hydrogen-fueled engine that combines the
best elements of air-breathing and rocket propulsion. It operates initially
as an air-augmented rocket as it accelerates to low supersonic speeds,
transitions to ramjet operation by turning off the rockets, then converts to
a scramjet as flight speed increases. The rockets are turned back on as
atmospheric oxygen diminishes, then the engine transitions to a
high-expansion rocket for final ascent.
During the initial program phase, the Strutjet RBCC demonstrated superior
performance and a robust operating capability in wind tunnel tests over the
entire flight operating range. Also, Aerojet's patented cascade fuel injector
efficiency and rocket durability and flexibility have been proven in the
large number of tests conducted.
Aerojet, a leading proponent of RBCC propulsion, has demonstrated excellent
performance using both hydrogen and hydrocarbon fuels, providing evidence of
the flexibility of this engine. Aided by Aerojet technology advances on this
program, NASA placed recent emphasis on continuing the advancement of this
promising concept through flight.
Aerojet, a leader in propulsion, electronics and weapon systems, and fine
chemicals, is a segment of GenCorp, a technology-driven company with strong
positions in polymer products, automotive, and aerospace and defense
industries.
* * *
Washington - August 12, 1999 - Researchers at NASA'ss Glenn Research Center
have made for the first time tiny particles of frozen hydrogen suspended in
liquid helium, a first step towards new rocket fuels that could revolutionize
rocket propulsion technology.
In the experiments, small amounts of liquid hydrogen were poured onto the
surface of liquid helium. The liquid hydrogen was at a temperature of 14
kelvins (minus 435 degrees F), just above freezing point; and the liquid
helium was held at 4 kelvins (minus 452 degrees F), or just above absolute
zero.
As the liquid hydrogen fell toward the surface of the helium, small, solid
hydrogen particles formed and then floated on the surface of the helium.
The suspension will be used to make futuristic atomic fuels that take
advantage of the chemical recombination of atoms into molecules.
"Atomic fuels will make possible rockets with liftoff weights one-fifth that
of today's or with payloads three to four times more massive," said Bryan
Palaszewski, Glenn principal investigator for the experiment.
Using atomic fuels could reduce or eliminate on-orbit assembly of large space
vehicles, thereby eliminating multiple launches and years of assembly time
and making flights to all parts of the solar system less expensive and more
practicable.
In atomic fuels, atoms of very active elements would be stored in a medium
that prevents their recombination. Solid molecular hydrogen is a promising
medium for storing and keeping atoms separate because it becomes solid at
temperatures just a few degrees above absolute zero, where atomic activity
due to heat is at a minimum.
Helium, in turn, is the ideal medium for creating and holding the solid
hydrogen particles because it remains liquid below the freezing point of
hydrogen. In the rocket's reaction chamber, or engine, the fuel would warm,
and the atoms would be freed.
In less than an instant, they would recombine into molecules, and
temperatures would go from 4 to 2000 kelvins (minus 452 to 3140 degrees F).
Both hydrogen and helium would instantly vaporize and shoot out of the engine
at tremendous speed, propelling the rocket forward.
Details about the behavior and characteristics of the particles are described
in a paper presented at the U.S. Air Force High Energy Density Materials
Meeting in Cocoa Beach, FL, in June of this year.
The advanced fuels experiments are part of Glenn's continuing efforts to
advance the state of the art of propulsion technology. The experiments were
conducted under the auspices of the NASA Advanced Space Transportation
Program (ASTP), led by NASA Marshall Space Flight Center, Hunstville, AL.
Current research is underway with an extensive team that includes researchers
from Glenn, Marshall, the U.S. Air Force, the Department of Energy,
universities and industry.
* * *
Fusion fuels dreams of space travel
Concepts could yield new propulsion techniques in a few years Terry Kammash,
an astrophysicist and engineer at the University of Michigan, is developing
a concept for a gas-dynamic mirror fusion propulsion engine.
By Anne Rueter
NEWHOUSE NEWS SERVICE
ANN ARBOR, Mich., Aug. 11-To Terry Kammash, going to the stars is not sci-fi
stuff. In the new millennium, the nuclear engineer envisions missions to
Alpha Centauri, closest star to our solar system. In just the next 20 to 25
years, he predicts spacecraft will reach one milepost on the route, the Oort
Cloud, a debris-filled comet belt 932 billion miles away. And he’s betting
the missions will use fusion, the basic energy source of stars themselves.
NEVER MIND that efficient fusion reactors to power industry and light our
homes have so far eluded scientists and engineers. Kammash has designed two
propulsion engines that take one of fusion’s serious flaws and turn it into
an asset for space travel. And as scientists search for ways to explore the
vast distances in space, Kammash’s most developed design looks like a
front-runner.
The physics is well understood, the technology is available, said Kammash, a
University of Michigan professor emeritus. It’s just a question of putting
it together.
That’s what NASA scientists have been doing at the Marshall Space Flight
Center in Huntsville, Ala., where several alternatives to chemical rockets
are being explored. Kammash’s concept is the furthest along, said Bill
Emrich, a senior engineer at the center. He’s getting a working model ready
to test the design the first such test of fusion propulsion for use in
space.
I think it’s a reasonably promising (concept), although there are others
that look promising too, Emrich said. It’s hard to say at this point which
one is going to be the winner.
FUSION IN A YEAR OR TWO?
Kammash’s gas-dynamic mirror engine holds promise for faster travel to
planets such as Mars and Pluto. Emrich and other NASA scientists have
electromagnets in place in a 2-meter-long model of the engine. In the next
few months, they hope to start injecting plasma, the superheated fuel that
the magnets are designed to confine long enough to produce nuclear fusion
reactions. The scientists hope to achieve fusion during the next year or
two.
Meanwhile, Kammash is pushing forward with his second engine design, one
with the thrust needed for more distant interstellar missions. He got a
boost recently when this design was among a handful of propulsion ideas to
receive funding from NASA’s newly formed Institute for Advanced Concepts.
Both engines, Kammash said, aim to cut to a realistic level the time and
cost of missions to planets in our solar system and beyond. And time is of
the essence. Using conventional chemical rockets, missions to Mars are long
enough to be daunting for humans: At seven to nine months each way, a trip
might last two years. At a typical shuttle speed of 17,600 mph, it would
take 168,000 years or more for a robotic mission to reach Alpha Centauri.
Kammash estimates his gas-dynamic mirror fusion propulsion engine would take
three to four months to travel to Mars and back. He thinks his newer design,
fast enough for interstellar missions, could reach Alpha Centauri, 259
trillion miles away, in as little as 213 years. This new engine might take a
mere 29 years to make a one-way trip to the Oort Cloud.
Now it costs $10,000 to put a kilogram in space, Kammash said. He and other
space scientists take seriously NASA’s challenge to cut this figure to
$2,000 or less. Alternative propulsion methods are key because conventional
fuels for long missions are extremely bulky and costly. It takes huge
amounts of fuel to lift a spacecraft into space if it must carry fuel to
travel to distant planets or stars.
OTHER OPTIONS
Fusion energy, produced when the light nuclei of certain atoms fuse together
under intense heat, is not the only energy source being eyed for
long-distance space missions. Energy from fission, the splitting of heavy
atoms, is still a contender. Fission rockets, though they evoke safety
concerns, haven’t been abandoned and could power missions to the relatively
near moon and Mars. For more distant ones, scientists believe fusion has
greater potential.
The idea of a robotic mission to explore the environs of Alpha Centauri
draws many skeptics, but also many restless minds eager to try. If man does
not explore he becomes stagnant, civilization becomes stagnant, Kammash
said.
Streams of leaking energy are one reason fusion hasn’t lived up to hopes as
an energy source on Earth. Some fusion reactors have had trouble producing
more energy than they lose because hot plasma, the system’s fuel, is hard to
contain. Kammash worked on designs for such fusion reactors for decades.
Fusion enthusiasm ran high in the late 1970s and early ’80s; now Congress
continues to reduce funds for fusion research.
In the early 1990s, Kammash came to see possibilities in fusion’s problems.
You want to eject hot plasma because that’s propulsion, Kammash said. Fusion
is inherently leaky, so let’s take advantage of it.
The gas-dynamic mirror engine relies on powerful magnets to create
electromagnetic fields that will confine plasma particles long enough for
sufficient fusion reactions to occur. Mirror refers to the magnetic fields
at each end that bounce particles back and forth. The engine retains some of
the plasma to keep the fusion reaction going, and lets a fraction of it
escape through a nozzle to produce thrust.
THE ANTIMATTER FACTOR
The second engine, called MICF (Magnetically Insulated Inertial Confinement
Fusion), uses a different method to achieve fusion. A laser beam zaps
BB-sized pellets of fuel, creating a hot plasma contained by a metallic
shell. The plasma should be contained long enough to lead to large energy
gains, Kammash writes in Ad Astra, a magazine read by astronauts and other
space enthusiasts.
His idea is a concept that brings together antimatter and fusion propulsion,
said Robert Cassanova, director of the Institute for Advanced Concepts. We
found that intriguing.
Instead of a laser, Kammash ultimately wants to use antimatter, an
experimental technique, to zap the fuel pellets. Giant particle accelerators
produce fleeting forms of antimatter. Scientists are trying to find ways to
trap one form, antiprotons, and use the energy they produce. Using a stream
of antiprotons instead of a bulky laser apparatus would make Kammash’s
design very attractive in space.
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