|The discovery of ice at both arctic and Antarctic, forever dark poles of moon was anticipated at the INEEL after the Department of Defense Clementine mission provided the first suggestive evidence, during 1994. The data from the NASA probe "Lunar Prospector" suggests there may exist as much as 10 Billion tons (tons, not gallons) of pure ice veins.
Scientists and engineers at the INEEL found a simple and relatively
inexpensive way to remove water ice from the lunar surface and place it
into orbit around earth. This engineering discovery would provide several
orders of magnitude larger quantities of propellant than all known affordable
Water would be used as the propellant in nuclear-heated steam rockets.
Such a rocket would haul rocket fuel payloads, such as ice, from the surface
of the moon into orbit. Solar-heated steam rockets would take the ice to
an orbit out of the moon's gravity and then into an orbit that just grazes
the atmosphere of the Earth. The orbit of the ice would slowly decay. The
result would be ice in orbit around Earth. Delivering this rocket fuel
or propellant to Low Earth Orbit could dramatically lower the cost of space
transportation. Rockets from Earth could rendezvous with the ice and use
it for rocket propellant.
|Lunar_Ice_Rocket INEEL engineers and scientists published the details of this scheme at the Joint Propulsion Conference in Seattle, June 1997. It used lunar south pole ice as the resource.
|A follow-up publication "Lunar South Pole Space Water Extraction and Trucking System" details a lunar south pole space water truck, which was presented at the 6th International Conference and Exposition on Engineering, Construction, and Operations in Space, 26-30 April 1998.
The architecture would use solar powered steam rocket propulsion for all the steps beyond the low lunar orbit. The solar options permits us to keep the nuclear system trapped in a deep gravity well in deep space. These are discussed below.
A program to develop the steam rocket at the INEEL is described.
Generating electricity in space handicaps all known alternatives.
A bottleneck step, launching ice from the surface of the moon to low lunar orbit, strongly favors a nuclear-heated steam rocket. All other known options require orders of magnitude more support and processing hardware to achieve the same results. Generating electricity in space causes the problem.
Generating electricity in space requires hardware that weighs about 1000 times more than that of the steam scheme. This means alternatives cost 1000 times more.
NASA and others suggested that one could use electrolysis to split the water, which would give hydrogen and oxygen gasses. These would then be refrigerated and condensed into the same cryogenic liquid rocket fuels used by the Shuttle. This approach requires that all the energy be supplied by electricity. This alternative would therefore cost about 1000 times more than the steam scheme.
The INEEL scheme DOES NOT use electricity as the energy source.
The objective is to fuel a propulsion system that takes payloads to GEO once they are delivered to LEO. Communication satellites operate at GEO (geosynchronous orbit). Rockets take payloads to LEO (low earth orbit). The propellant or fuel would be water obtained from the North or South poles of the moon.
(click for hi res image)
Using water to take payloads from LEO to GEO uniquely provides a path for cash flow, to pay for such space resource utilization schemes.
Easy access to GEO means faster wireless internet connections.
Steam rockets use water
A steam rocket is a rocket with water vapor exhaust. The Shuttle main engines burn LOX and Liquid Hydrogen LH2 to produce steam exhaust.
The nuclear-heated option provides an exceptionally simple architecture. A relatively small nuclear heater provides enough energy to heat shovel plates to cut through the extremely cold, 80 Kelvin permafrost. A small nuclear electric generator would provide 100 Kilowatts for headlights, computers and communications. It would weigh several tons mass and shed 3 Megawatts of "waste" heat. A small nuclear heater (3 Megawatts) provides the heat (3.5 megajoules per kilogram) needed to vaporize the ice (27,000 tons per year) to room temperature vapor. A condenser collects the pure water.
The nuclear-heated steam rocket then uses the water as propellant to
launch payloads to low lunar orbit.
Compressing and refrigerating the gaseous oxygen and hydrogen to make them liquid cryofuels also takes compressors and heat sinks. The refrigerator for the LH2 requires more electricity than splitting water, and is not very efficient because LH2 is at 22 Kelvin.
The chemical option is complex and requires massive hardware to deliver comparable payloads to LLO.
The only advantage of the chemical option is that it uses about 3 times less water than the nuclear option.
A nuclear heated steam rocket to develop this specific power needs to provide a mixed mean outlet steam temperature into the nozzle of about 1100 Kelvin. This is half the temperature of the NERVA rocket (> 2500 Kelvin) demonstrated during the late 1960's. The specific power density in the core is something between 1 and 3 megawatts per liter of reactor core. The specific power is less than that of NERVA (3 megawatts per liter).
Technical Details and Background
|An INEEL scientist first proposed using ice from space at the First International Conference on Near-Earth Asteroids, June 1991. Another paper presented at the World Space Conference, 1992, detailed how steam rockets heated by nuclear reactors would use water ice taken from a little known and accessible comet formation in the space between Mars and Jupiter to transport tens of thousands of tons of payload. The payload would have been more water ice, or possibly the hydrocarbons found on comets. The destination was an orbit around Earth itself.
This does NOT minimize the amount of propellant used. The optimum specific velocity results in the propellant requirement of about 4 times the payload. The assumption is that
However, energy is not free. And peak power is definitely not free. This situation favors all propulsion processes that use heat alone, and strongly dis-favors processes that require electricity.
The unexpected result of the thermal-rocket equation is that the optimum favors steam rockets for lower delta-V missions. "Lower delta V" means under about 4000 m/s. INEEL scientists published architectures for such missions, (click here for architecture image) which included going to Mars from a high earth orbit, going to the outer edge of the asteroid belt from a high earth orbit, for delivering payloads from Low Lunar Orbit to GEO, or for going from LEO to GEO.
Further, water has a uniquely low (7 mm Hg) vapor pressure just above
its melting point. This permits tankage fractions under 1%. Extracting
water from space ice requires only a room temperature thermal process.
INEEL scientists and engineers determined that the current state of the art of water cooled nuclear systems strongly suggests the required system can be constructed. The 4 engineering options identified for nuclear fuel elements are:
Concept 2: An annular fuel, BWR-like design that exploits a relatively straightforward extension of Concept 1. The use of annular fuel will limit peak fuel temperatures in the solid cylindrical rods of Concept 1. The fuel inside the annulus can be solid,liquid or gaseous This concept also provides automatic axial power flattening during life and provides an easy mechanism to control radial power flattening during the design process.
Concept 3. Steel clad plate fuel design. Can utilize flat (or curved) plate fuel to increase achievable heat transfer and therefore increase power density. Same principle as utilized in the ATR.
Concept 4. Particle bed design inherently provides an exceptionally high heat transfer capability and therefore an exceptionally high power density. This concept provides the potential for the highest performance but at the cost of the highest technology development with inherent costs and risks.
A program to develop the nuclear fuels and a high-peak power nuclear reactor would have the following elements:
4. Nuclear Testing Of Fission Heated Fuels
The current experience base is not adequate to project how mundane (or how exotic) an approach might be required to achieve an adequate power density and power-to-weight ratio in a reactor utilizing approximately 1100 K steam as the coolant and propellant. Concept definition and evaluation work is required to estimate what performance can be achieved.
Four concepts have been identified for preliminary evaluations. The first draws heavily on the existing reactor technology base. The fourth offers exceptionally high performance potential but also represents the greatest technology development effort.
Serial evaluation of the concepts is proposed. Evaluation of the first
may yield performance estimates that suggest moving immediately to the
fourth concept. Evaluation of the first may also indicate adequate performance
is achievable with the first and suggest moving immediately to Phase II
for Concept Development and Evaluation.
Thermal and heat transfer analysis - Thermal, heat transfer, and fluid flow analysis will have to be conducted for every specific reactor core configuration and balance of system. Questions to be addressed in these analyses include how efficiently core energy generation is transferred to the cooling medium and how reactor operating conditions and environment influence the thermal and thermal hydraulic conditions at the nozzle entrance. In essence, hand calculations along with analysis using current reactor design and performance codes (such as RELAP5) will be used to examine the performance and behavior of the reactor and system for a wide variety of steady-state and transient operating conditions. Given the plausibility of new fuel designs, literature will have to be searched to find appropriate correlations to support this analysis. Clearly, these calculations will be iterative in nature as the design concepts continue to develop. Thermal analysis must also be conducted to estimate the performance of the nozzle attached to the reactor. Through a combination of hand calculations and computational fluid dynamics analysis, a map of the nozzle performance (e.g. ISP) as a function of thermal-hydraulic conditions (e.g. temperature, quality, flowrate, void fraction, pressure) at the nozzle entrance will be generated. This map will be generally useful in that the results should be independent of the reactor concept for the most part.
Mechanical Design - Mechanical design will be conducted for each configuration proposed. This task essentially determines what the various reactor components are and how the components fit together to compose a working system. Details of component equipment pieces (such as pumps), piping system design and layout, packaging, control system, and so forth will be defined in this task.
Mechanical/Stress Analysis - As with any design, analysis must be conducted to address the performance of the materials and components of the system to ensure that they are not unnecessarily overloaded or over stressed during the design life of the system. Many factors must be considered including the fuel, fuel cladding, fuel support structure, piping, piping support system, nozzle, and so forth.
Other tasks supporting the above will be required. These tasks include:
Safety - We will need to develop a Safety Program Plan
similar to that for the Multi-Megawatt Space Reactor Program. This
Plan should address the top-level safety requirements, how safety will
be managed and control within the program, who will have what safety responsibilities,
what safety documents will have to be generated, and what safety milestones
and schedules have to be met. Safety interface requirements with humans
and potential NASA launch
vehicles will have to be defined. A Safety Plan for the Concept Development Project should also be developed which relates the overall Safety Program Plan to specific design concepts and lays out safety
requirements for each. Real work, as Bruce describes it, would involve developing potential safety approaches for each concept and performing preliminary fault tree analyses, failure modes and effects analyses,
criticality analyses, etc. on the preliminary design concepts.
Function and Operations - As mentioned above, detailed requirements for all aspects of the project must be developed and maintained. This includes functional and operational specifications, safety requirements, disposal requirements, and so forth.
Materials Testing - New materials or derivatives of existing materials may have to be developed to support the mechanical and operational requirements and needs of the concept design. Materials for cladding, nozzle, piping system, etc. will need to be examined in high temperature, corrosive steam environments similar to that expected during reactor operations to determine material performance. The INEEL Supercritical Water Oxidation Loop may well be capable of doing coupon testing required to support these needs.
Mission Development - Mission profiles and plans will likely
be developed by other participating agencies. However, the INEEL must remain
closely involved in these developments. First, it must be ensured that
mission profiles fit within the assumed/established requirements for the
reactor designs being considered. Second, the INEEL needs to remain in
the decision making process associated with the profile developments to
ensure that the best interests of the INEEL can be realized and future
prospects can be capitalized on.
Based on the above discussions and preliminary task definitions, 16
FTEs for 1.5 years would be necessary to effect the conceptual reactor
strategic: don yurman
systems: dave nipper, lyn parlier
extraneous elements deleted because they are obvious to all:
Project Management - A capable project manager will be required to coordinate and ensure the project goals are accomplished within schedule and budget limitations and that a team environment is maintained.
- A visionary will be required to help expose the project, define the limits,
ensure a broad support base for it, lead the project in the directions
consistent with the best interests of those involved, and protect the project.
It is expected that the Chief Scientist would help develop beneficial collaborations
with appropriate entities (such as NASA, other Labs, commercial entities,
etc.) and help develop and maintain the funding base.