New Mars Forums

Did you ever notice that your posts are full of things you claim that I said but when you, oh you know actually read my posts then mysteriously it turns out that I never said any of them? Its not very healthy from a mental stand point that these are the very issues that you obssess about the most.

Then you said "Basically you claim that contemporary reactor technology will reach an impossibly high level of performance through "R & D," I dare you to prove that I ever in my life said that. Hey what happens to authors that present falsified data as fact. (by the way, thanks for further validating my assessment of your alleged research issues.....just keep on posting now....show everybody what you've got!).

Although it is possible that this level of quality is what passes for rearearch in whatever world you live in (outlandish assertion, take my dare and then decide for yourself!

I'll admit that you are right when you say that peer review is 100% valid as a
process. I enjoy it and have made use of it many times myself. I just think that you might want to submit your own posts to it (a little introspection is good for the soul).

Personally, if I were the one proposing Gas Core Nuclear reactor technology as a viable alternative to well, anything at all, I wouldn't feel comfortable calling other peoples posts into question. Your  advocacy of gas core technology certainly validates your ability to do reasearch?????? Speaking of someone backing up their claims, why don't you post some objective, third party, verifiable information on the existance, engineering specifications, known performance specifications and operating history of say one or more gas core reactor that have been built......ever.

Enough said, about whether or not you are qualified to question anyone about anything, anywhere. ever.

Dude, you clearly have some sort of a problem. Thats OK though, I would suggest that you take a short break from posting in this forum and relax, take it easy maybe get a head C-T or something. I'm sure inthe long run everything will stabilize and you'll be OK....someday.

Chazbro

Try googlig the Toshiba S4 reactor. It only produces 10MW and doesn't weigh anywhere near 250 MT. But its a safe bet that any megawatt class reactor is going to be heavy. Power/Mass density issues will just have to handled through ongoing R & D. As for complicated, any Nuclear reactor that actually EXISTS will, in fact be complicated I can pretty much asure you of that. Thats one of the advantages of actually having to deal with them first hand instead of only reading about them. I Understand their complexity. I guess any reactor that actually EXISTS will be far more complex than a reactor technology that doesn't----I concede that point!

Chazbro

Toshiba, which designs a small nuclear reactor named 4S (for "Super Safe, Small, & Simple"),
The 4S is a sodium-cooled fast spectrum reactor -- a low-pressure, self-cooling reactor. It will generate power for 30 years before refueling

Toshiba, which designs a new 10-megawatt nuclear reactor costs about $ 25 million

Pay the operating costs, estimated at 10 cents a kilowatt-hour
. There are no complicated control rods to move through the core to control the flow of neutrons that sustain the chain reaction; instead, the reactor uses reflector panels around the edge of the core. If the panels are removed, the density of neutrons becomes too low to sustain the chain reaction.
Designers chose sodium so they could run the reactor about 200 degrees hotter than most power reactors, but still keep the coolant depressurized.
It will use uranium enriched to 20 percent and generate power for 30 years before needing to be disposed of and replaced.
This special 'you don't need to do anything to keep it going safely' feature of the reactor is to be found in the way that the operating system has been reduced to the simplest possible level. For example, the primary coolant pump which transports the heat generated in the nuclear fuel is a component installed inside the reactor vessel. What is more, it uses liquid sodium as the coolant, which means it can use an electromagnetic pump with no moving parts. That is one reason why it can continue operating for as long as 30 years. The heat of sodium, primary coolant, is transferred through a heat exchanger to a secondary coolant, and that heat exchanger is also inbuilt inside the reactor vessel.

One more unique feature of this reactor is that there are no control rods for controlling the nuclear reaction, though existing medium- and large-sized reactors have control rods. In place of the control rod, an annular reflector which is used for reflecting the neutrons produced by nuclear fission so they can be used efficiently, moves up and down inside the reactor vessel, controlling the nuclear reaction over the long term, over the short term, as well as moment by moment.
For a space power system, high reliability and low specific weight and volume are driving requirements. Efficiency is important to the extent that it influences system weight and low efficiency places extreme requirements on the energy source. Liquid metal MHD is a passive energy conversion process and thereby minimizes the number of rotating components. A liquid metal cooled fast reactor provides the heat source for the liquid metal MHD working fluid, while retaining a relatively compact core configuration for this range of powers. The power system studied is based on a two phase flow liquid metal MHD generator with lithium as the electrodynamic fluid and helium as the thermodynamic fluid.

Chazbro

Who is Robert?

Any how, NASA astronaut Scott Horowitz claims to have run the performance numbers of the SRB on his computer and found that, in his words, it would be “a hell of a ride.” The SRBs burn out after just over two minutes, and although powerful, a single SRB doesn’t have enough performance alone to put a manned spacecraft into orbit. At burnout “you’re going about Mach 18 and pulling about TWENTY g’s,” he said. So much for man-rating the SRB's!

(I assume that a man-rating assumes that a man inside would actually survive the trip to LEO--but I could be mistaken about that little detail. Maybe someone could set me straight on that!)

In addition, turning the SRB into a launch vehicle requires an upper stage.

Despite the discussion within NASA and elsewhere about using the SRB to launch the CEV, it’s not clear whether there’s sufficient momentum behind the idea to at least allow further studies, let alone selection of the concept for development. ATK Thiokol is strongly behind the idea because it gives new life for the SRB—a significant portion of their business—once the shuttle is retired around the end of the decade(Thiokol is behind this absurd concept, Oh there's a surprise!).

There are other technical issues that a SRB-derived launch system would have to address, notably the development of a new upper stage. However, in the long run the bigger challenges that an SRB-based launcher might have to face are perceptions: that the SRB is an old technology, best left to the past; that solid-propellant motors like the SRB, which can’t be turned off once ignited, are unsuited for manned spaceflight applications. All of this equals more billions spent and more years of delay for a CEV. I guess I'm answering my own question!

People, people, the current SRB as a first stage is a technical impossibility for one simple reason, its design is incompatible with open loop guidance and control.

You have to remember that it was developed exclusively to be an integral component of a FOUR piece stack. 95% of the guidance, control, load balancing and of course the THROTTLING capability of that stack was provided by the orbiter.

If you are still confused, just remember the corkscrew contrail that resulted after the Challenger explosion and that SRB's prematurely seperated and flew off on their own. They are designed with extremely limited control capability based on gimballing the thrust nozzle along only axis between 0 and 180 degrees.

I would like anyone to explain how the current SRB can overcome these technical/engineering deficiencies to provide a capabilty as a man-rated 1st stage.

For anything other than Cis-lunar travel, chemical propulsion is ABSURD. Six months or more each way to Mars isn't particularly feasible either(I've been on multiple patrols on nuclear-powered ballistic missile submarines for three months at a time and thats pretty close to the limit). Nuclear electric propulsion is over 10 times more efficient than chemical rockets so clearly either Ion drives or VASIMR or the only realistic alternatives at this time. A nuclear electric propulsion system could propel and power at least ten times as much payload science as any chemical system of comparable mass. In a nuclear electric propulsion system, a nuclear reactor produces heat, a power-conversion system converts the heat to electricity, and an ion thruster (or VASIMR) uses the electricity to propel the spacecraft. The new generation of Nuclear Electric Propulsion Systems(NEPS) are  designed to last seven to 10 years in space and are about 15 times more efficient than the Space Shuttle Main Engines.
"The more efficient the engine, the less fuel the spacecraft has to carry. As for nuclear reactor technology I refer everyones attention to RAPID (Refueling by All Pins Integrated Design) The 200 kWe uranium-nitride fueled lithium cooled fast reactor concept (RAPID-L 1) The 200-kW (electric) uranium-nitride-fueled lithium-cooled fast reactor concept "RAPID-L" to achieve highly automated reactor operations. RAPID-L is designed for space based power systems. It is one of the variants which enables quick and simplified refueling. The essential feature of the RAPID concept is that the reactor core consists of an integrated fuel assembly instead of conventional fuel subassemblies. In this small-size reactor core, 2700 fuel pins are integrated and encased in a fuel cartridge. Refueling is conducted by replacing a fuel cartridge. The reactor can be operated without refueling for up to 10 yr. RAPID-L Operator Free Fast Reactor Concept Without Any Control Rods.

People should check their facts before they post on this topic.

Charlie

There is of course one simple solution to all of these issues. I call it the management of manned deep space flight hygiene. Minimize exposure time to cosmic rays, zero-g effects and isolation thorough the use of powerful propulsion systems that get you to Mars in the shortest amount of time possible. It removes the need for extensive radiation shielding and or complex rotating structures.

I think you'll find that for the short term this is the only realistic way to go.

Charlie

There are probably thousands of unemployed if not bored to tears
Russian space scientist, engineers and the like out there. Shouldn't we be inviting them to contribute to some of our forums?

Are there any Mars society chapters in Russia or the former Soviet union?

As a former submariner I can tell you that they had some pretty innovative science and engineering going on in Russia and I can't recall having seen any posts from anyone in that part of the world

Whats up with that?

Charlie

The implementation of a supersafe, supercompact lithium-cooled fast reactor which features fully automated reactor operation.
A reactor with a fully automated operational capability from startup to shutdown in order to ensure extremely high safety by eliminating human errors. The new design does not use control rods. Instead, it employs newly developed systems such as the Lithium Expansion Module (LEM) for the control of reactors by utilizing the thermal expansion of liquid lithium 6, which is a neutron absorber, a Lithium Injection Module (LIM) for shutting down the reactor and a Lithium Release Module (LRM) for starting it up.

For the high-performance thermoelectric energy conversion system with a twice or better performance than previous systems, which will be adopted as the power conversion system, an op- erational test has been conducted under the temperature condition of 1,000¡ëC.
With a thermal power of 5,000 kW and electric power of 200 kW, the output of this reactor is much smaller than large power-generating reactors. However, it has a very compact size and the very low total weight of 7.6 tons and it is capable of continual operation without refueling for ten years. Potential uses for RAPID-L are in power plants in urban areas of industrialized nations to relieve the peak load, and for developing countries where remote regions cannot be conveniently connected to the main grid and where it is economical to provide local generation capacity.
Also this reactor can be applied as a power source for lunar base where neither air nor water is available and maintenance by astronauts would be difficult. The 200-kW(electric) uranium-nitride-fueled lithium-cooled fast reactor concept "RAPID-L" to achieve highly automated reactor operation has been demonstrated. RAPID-L is designed for a lunar base power system. It is one of the variants of the RAPID (Refueling by All Pins Integrated Design) fast reactor concept, which enables quick and simplified refueling. The essential feature of the RAPID concept is that the reactor core consists of an integrated fuel assembly instead of conventional fuel subassemblies. In this small-size reactor core, 2700 fuel pins are integrated and encased in a fuel cartridge. Refueling is conducted by replacing a fuel cartridge. The reactor can be operated without refueling for up to 10 yr.

Unique challenges in reactivity control systems design have been addressed in the RAPID-L concept. The reactor has no control rod but involves the following innovative reactivity control systems: lithium expansion modules (LEM) for inherent reactivity feedback, lithium injection modules (LIM) for inherent ultimate shutdown, and lithium release modules (LRM) for automated reactor startup. All these systems adopt 6Li as a liquid poison instead of B4C rods. In combination with LEMs, LIMs, and LRMs, RAPID-L can be operated without an operator.

Scientists at Ben-Gurion University of the Negev have shown that an unusual nuclear fuel could speed space vehicles from Earth to Mars in as little as two weeks. Standard chemical propulsion used in existing spacecraft currently takes from between eight to ten months to make the same trip. the fairly rare nuclear material americium-242m (Am-242m) can maintain sustained nuclear fission as an extremely thin metallic film, less than a thousandth of a millimeter thick. In this form, the extremely high-energy, high-temperature fission products can escape the fuel elements and be used for propulsion in space.

Obtaining fission-fragments is not possible with the better-known uranium-235 and plutonium-239 nuclear fuels: they require large fuel rods, which absorb fission products.

Of the known fission fuels, Am-242m is the front-runner, requiring only 1 percent of the mass (or weight) of uranium or plutonium to reach its critical state. The recent study examined various theoretical structures for positioning Am-242m metal and control materials for space reactors.

There are several ways of getting nuclear thrust effects. This method uses the energy of the atom fragments as well. In fission-fusion bombs special beryllium-copper mirrors direct these fission products, X-rays, neutrons, and etc. down beam channels to fire the secondary system.

In the ORNL fireball type reactor much of the relativistic energy is released as well, in the form of neutrons, x-rays, and gamma rays. Similarly, these emissions can be reflected using mirrors from omnidirection emissions into directed emissions. The net effect is similar to ion drive system, except vastly more powerful.

Dr. Chang-Diaz has lead the development of a high-power, electrothermal plasma rocket — the variable-specific-impulse magnetoplasma rocket (VASIMR) — that is capable of exhaust modulation at constant power. An electrodeless design enables the rocket to operate at power densities much greater than those of more conventional magnetoplasma or ion engines. An aspect of the engine design that affords a capability to achieve both high and variable specific impulse (Isp) places the VASIMR far ahead of anything available today. Inasmuch as this rocket can utilize hydrogen as its propellant, it can be operated at relatively low cost. Because the VASIMR uses plasma to produce thrust, it is related to several previously developed thrusters; namely, the ion engine, the stationary plasma thruster (SPT) (also known as the Hall thruster), and the magnetoplasmadynamic (MPD) thruster [also known as the Lorentz-force accelerator (LFA)]. However, the VASIMR differs considerably from these other thrusters in that it lacks electrodes (a lack that enables the VASIMR to operate at much greater power densities) and has an inherent capability to achieve high and variable Isp. Both the ion engine and the SPT are electrostatic in nature and can only accelerate ions present in plasmas by means of either (1) externally applied electric fields (i.e., applied by an external grid as on an ion engine) or (2) axial charge nonuniformity as in the SPT. These ion-acceleration features, in turn, result in accelerated exhaust beams that must be neutralized by electron sources strategically located at the outlets before the exhaust streams leave the engines.
In the LFA, acceleration is not electrostatic but electromagnetic. A radial electric current flowing from a central cathode interacts with a self-generated azimuthal magnetic field to produce acceleration. Although LFAs can operate at power levels higher than those of either the ion engine or the SPT and do not require charge neutralization, their performances are still limited by the erosion of their electrodes.
An MPD plasma injector includes a cathode in contact with the plasma. Although the plasma at the location of contact is relatively cold, the cathode becomes eroded and the plasma becomes contaminated with cathode material (typically tungsten). The erosion and contamination can contribute to premature failure and to increased loss of energy through radiation from the contaminants in the plasma. An equal limitation on performance is exerted by nonionized propellant in a high-power amplifier cavity that is part of the MPD; the reason for this limitation is that neutral atoms and molecules in this region lead to charge-exchange losses, which, in turn reduce the overall efficiency of the engine and increase the unwanted heat load on the first wall (the liner) of the MPD thruster.
The design of the VASIMR avoids the aforementioned limiting features. The VASIMR contains three major magnetic cells — the forward, central, and aft cells. A plasma is injected into these cells, then heated, then expanded in a magnetic nozzle. (The magnetic configuration is of a type known as an asymmetric mirror.) The forward cell handles the main injection of propellant gas and an ionization system; the central cell serves as an amplifier to further heat the plasma to desired magnetic-nozzle-input conditions; and the aft cell acts as a hybrid two-stage magnetic nozzle that converts the thermal energy of the fluid into directed flow while protecting the nozzle walls and allowing efficient detachment of the plasma from the magnetic field. During operation of the VASIMR, a neutral gas (typically, hydrogen) is injected into the forward cell, where it is ionized. The resulting plasma is then heated in the central cell, to the desired temperature and density, by use of radio-frequency excitation and ion cyclotron resonance. Once heated, the plasma is magnetically and gas-dynamically exhausted by the aft cell to provide modulated thrust. Contamination is virtually eliminated and premature failures of components are unlikely.

The VASIMR offers numerous advantages over the prior art:
Its unique electrodeless design provides not only high thrust at maximum power but also highly efficient ion-cyclotron-resonance heating, and high efficiency of the VASIMR regarded as a helicon plasma source.
Because the VASIMR operates at relatively high voltage and low current, its mass is relatively low. This means that a one-ship human mission will not depend on a high-energy, complex rendezvous near Earth to achieve escape velocity. Instead, a rapid interplanetary transfer will be achieved with an adaptable exhaust, which will provide optimal acceleration throughout the mission.
The residual magnetic field of the engine and the hydrogen propellant will be effective as a shield against radiation.
Because of its continuous acceleration, the VASIMR will be able to produce a small amount of artificial gravitation, thereby reducing the physiological deconditioning produced by weightlessness.
The variability of thrust and Isp at constant power will afford a wide range of capabilities to abort.
Because hydrogen is the most abundant element in the universe, the supply of hydrogen could likely be regenerated in situ.

Variable Specific Impulse Magnetoplasma Rocket (VASIMR)

A 10-month one-way trek to Mars -- the standard assumed for today's chemical rockets -- would be reduced to just four months.

The lab director is NASA astronaut Franklin Chang-Diaz, a long-time plasma rocket believer who has been hard at work on the idea since 1979. He holds a doctorate in applied plasma physics and fusion technology from the Massachusetts Institute of Technology (MIT). Chang-Diaz terms VASIMR "a power-rich, fast-propulsion architecture"

The concept first jelled at Charles Stark Draper Laboratory in Cambridge, Massachusetts, then was picked up at the MIT Plasma Fusion Center before moving to JSC.

·    A VASIMR rocket system consists of three major magnetic cells denoted as "forward," "central" and "aft." To get the rocket roaring, a neutral gas, typically hydrogen, is first injected at the forward-end cell of the motor and ionized. This electrically charged gas is then heated to create a desired density in the engine's central cell. The heating is done by the action of electromagnetic waves, similar to what happens in a microwave oven, after heating, the plasma -- essentially a superheated gas -- enters a two-stage hybrid nozzle at the aft-end cell. Here the plasma detaches from the magnetic field and is exhausted to provide "modulated" thrust. This VASIMR configuration guides and controls the plasma over a wide range of temperatures and densities.