Patent Application
20240013939
Aspects of the present disclosure generally relate to a space system and, more specifically, to a space reactor system configured to be safely launched into space and method of use thereof.
Although the regulations for launching space-nuclear systems has technically changed in the last several years due to a pair of presidential memoranda (President of the United States, Presidential Memorandum on Launch of Spacecraft Containing Space Nuclear Systems, Washington, D.C.: White House, 2019; and President of the United States, Memorandum on the National Strategy for Space Nuclear Power and Propulsion (Space Policy Directive-6), Washington, D.C.: White House, 2020), there is a great deal of skepticism and hesitancy in the nuclear industry with regards to launching nuclear reactors into space.
The new directives break nuclear system launches into three tiers (See the 2019 Presidential Memorandum referenced above). The first tier applies primarily to radioisotope systems that cannot go critical (in the sense of self-sustaining fission reactions). This first tier refers to International Atomic Energy Agency (IAEA) safety requirements (See International Atomic Energy Agency, Regulations for the Safe Transport of Radioactive Material, 2018 Edition, International Atomic Energy Agency, 2018), namely:
Many nuclear propulsion concepts have been proposed over the decades, using the heat from a reactor or radioisotope to either generate electricity for an electric thruster, or directly heat a propellant. In the case of the latter, the specific impulse is severely limited by the temperature of the materials and lifetime is limited by the corrosive nature of the low molecular weight propellants (such as hydrogen). In the case of the former, the reactor requires a heavy power conversion system such as Brayton or Rankine conversion with complex and expensive components that are difficult to make reliable enough for a spacecraft. Additionally, the nuclear-electric system requires a massive heat rejection system to dump waste heat, and heavy shielding to protect the payload from gamma-rays and neutrons.
While radioisotope thrusters have also been proposed, to date they require isotopes produced on Earth and integrated with a thruster during manufacturing. This conventional approach restricts the options to isotopes that are longer lived that may be handled and launched before expiration (such as Pu-238, or Po-210). However, longer lived isotopes have very low activity (low power density) and, due to practical and safety limitations, the thrusters are quite small and low thrust. Only one known thruster concept has a relatively high-power density due its use of a shorter-lived alpha emitter such as Po-210 to generate a high-voltage potential between electrodes in an electrostatic thruster (See U.S. Pat. No. 3,184,915 to Low et al, incorporated by reference in entirety for all purposes).
Thus, a space reactor system and use method to overcome the above limitations would be desirable.
The following presents a simplified summary relating to one or more aspects and/or embodiments disclosed herein. As such, the following summary should not be considered an extensive overview relating to all contemplated aspects and/or embodiments, nor should the following summary be regarded to identify key or critical elements relating to all contemplated aspects and/or embodiments or to delineate the scope associated with any particular aspect and/or embodiment. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects and/or embodiments relating to the mechanisms disclosed herein in a simplified form to precede the detailed description presented below.
In an embodiment, a modular space reactor includes a plurality of sections, each section containing a component of an assembled reactor. Each section contains contents configured to be unable to sustain a fission chain reaction as an individual section and is configured to be separately launched into space from each other section. The sections are configured for assembly in space to form the assembled reactor configured for sustaining an active fission chain reaction only when all of the sections are assembled together.
In embodiments, contents of at least one section include at least one of fissile fuel, reactivity control devices, neutron reflectors, neutron moderators, radiation shielding mechanisms, cooling systems, power conversion systems. In embodiments, the sections are further configured for disassembly in space for being separable for at least one of refueling, decommissioning, and disposal of the system so disassembled.
In accordance with another embodiment, a method for providing a space reactor includes designing a modular space reactor including a plurality of sections, fabricating the plurality of sections, and separately launching into space each one of the plurality of sections from each other one of the plurality of sections. The method further includes assembling the plurality of sections in space to form the space reactor, and activating the space reactor so assembled. Each one of the plurality of sections is configured to be unable to individually sustain a fission chain reaction, and the space reactor is configured to be capable of sustaining an active fission chain reaction only when all of the plurality of sections are assembled together.
In certain embodiments, assembling the plurality of sections in space includes performing at least one of automatic rendezvous, manual rendezvous, and proximity operations to bring together the plurality of sections.
In other embodiments, assembling the plurality of sections in space includes at least one of docking, robotic assembly, manual assembly by remote control from astronauts in space, and manual assembly physically by astronauts in space.
In a further embodiment, assembling the plurality of sections in space includes coupling together at least one of electrical harnesses, fluid lines, gas connections, heat transfer structures, and additional equipment, devices, and structures associated with the reactor system.
In accordance with another embodiment, a modular space reactor includes a plurality of sections, each section containing a component of an assembled reactor. Each one of the plurality of sections contains contents configured to be unable to sustain a radioactive chain reaction as an individual section, and each one of the plurality of sections is configured to be separately launched into space from each other one of the plurality of sections. In embodiments, the plurality of sections are configured for assembly in space to form the assembled reactor, and the assembled reactor is configured for sustaining an active radioactive chain reaction only when all of the plurality of sections are assembled together.
In certain embodiments, contents of at least one of the plurality of sections include at least one of radioactive isotopes, reactivity control devices, neutron reflectors, neutron moderators, radiation shielding mechanisms, cooling systems, power conversion systems.
In embodiments, the plurality of sections are further configured for disassembly in space for being separable for at least one of refueling, decommissioning, and disposal of the system so disassembled.
In a further embodiment, a method for providing a space reactor includes designing a modular space reactor including a plurality of sections, fabricating the plurality of sections, and separately launching into space each one of the plurality of sections from each other one of the plurality of sections. The method further includes assembling the plurality of sections in space to form the space reactor, and activating the space reactor so assembled. In embodiments, each one of the plurality of sections is configured to be unable to individually sustain a radioactive chain reaction, and the space reactor is configured to be capable of sustaining an active radioactive chain reaction only when all of the plurality of sections are assembled together.
In certain embodiments, assembling the plurality of sections in space includes performing at least one of automatic rendezvous, manual rendezvous, and proximity operations to bring together the plurality of sections. In other embodiments, assembling the plurality of sections in space includes at least one of docking, robotic assembly, manual assembly by remote control from astronauts in space, and manual assembly physically by astronauts in space. In further embodiments, assembling the plurality of sections in space includes coupling together at least one of electrical harnesses, fluid lines, gas connections, heat transfer structures, and additional equipment, devices, and structures associated with the reactor system.
These and other features, and characteristics of the present technology, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular form of ‘a’, ‘an’, and ‘the’ include plural referents unless the context clearly dictates otherwise.
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the embodiments detailed herein. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the described embodiments. The same reference numerals in different figures denote the same elements.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustrations or specific examples. These aspects may be combined, other aspects may be utilized, and structural changes may be made without departing from the present disclosure. Example aspects may be practiced as methods, systems, or apparatuses. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims and their equivalents.
The embodiments described in the present disclosure overcomes the significant limitations of conventional nuclear propulsion concepts to include conventional radioisotope thruster concepts operated in space.
In an embodiment, two or more fueled disc sections are launched separately, then coupled end-to end (axially) in space. Two or more disc-sections are required for the reactor to go critical (i.e., sustain a fission chain reaction). One or more sections may contain portions of the reactor control system and instrumentation. Each section is designed so that it cannot (under any plausible scenario or launch accident) sustain a fission chain reaction.
It is recognized herein that the A2 values from Table 2 in the IAEA 2018 publication cited above for uranium 235, 238 and LEU are unlimited. This requirement plus the requirements for Tier I suggest that small amounts of fissionable fuel could be launched (i.e., in quantities small enough that it is physically impossible to achieve criticality) under Tier I. Therefore, in accordance with certain embodiments, a space nuclear reactor may be launched in multiple pieces on separate launch vehicles and assembled in space (e.g., in a stable nuclear-safe orbit) while satisfying the requirements of Tier I and avoid incurring the additional safety reviews of Tier II. Certain embodiments of this concept are described immediately hereinafter.
Examples of possible reactor launch configurations are further described below. An important feature is that the individual reactor sections/fuel loads are designed so that they cannot sustain a fission chain reaction under a variety of anticipated plausible scenarios, such as submersion in sea water (which would moderate neutrons), compression from a launch explosion (which increases fuel density), or other possible launch accident. This objective may be accomplished done by reducing the quantity of fissile material in any single launch so that achieving a critical mass would be essentially impossible. Reducing the fuel quantity per launch also reduces the risk of the fuel container(s) failing in a launch accident, since each container(s) may be made more robust, as well as the amount of radioactive material that can spread into the environment in case of a catastrophic failure. To remain within the requirements of Tier I, the uranium fuel must also be low-enriched (e.g., below 20% enrichment).
Various embodiments described herein involve the separate launch of two or more separate sections/fuel loads (e.g., on separate launch vehicles) and combined in space. Many solid-fuel particles or fuel elements (for example, fuel pebbles for a pebble-bed reactor), may be delivered to the reactor in space in multiple loads launched separately from one another, such that each load by itself cannot sustain a fission chain reaction under any plausible scenario or launch accident. The fuel elements may be placed in the reactor using a variety of coupling mechanisms. When the reactor contains enough fuel, it can go critical. Several examples of modular space reactors are illustrated below.
In embodiments, each one of disc sections is launched separately in a launch vehicle, such as a rocket (not shown in
The variety of control elements and instrumentation (e.g., control rods, drums, discs, and/or other reactivity control mechanisms) may be split among different disc sections, or contained within one or a few of the disc sections. Similarly, any cooling system components (e.g., pumps, heat pipes, channels for fluid coolant, and/or other heat transfer devices) may be split among the disc sections or contained within one or a few of the disc sections. Conversely, any control or coolant devices may be separate from the disc sections, and only added during or after assembly. Other components or systems used in association with reactors, such as fissile fuel, reactivity control devices, neutron reflectors, neutron moderators, radiation shielding mechanisms, cooling systems, power conversion systems (or subsystems that may be disposed on different disc sections then assembled) may also be launched within one or a few of the disc sections then assembled together in space, and such configurations are considered to be a part of the present disclosure. Assembly of the disc sections may be performed autonomously (e.g., in a self-assembly manner, using pre-programmed autonomous means, or by robots or the like), by remote control by humans in space or on the ground, or manually by humans in space (e.g., astronauts). The assembly process may be performed using, for example, rendezvous and docking procedures or by other mechanisms for safely and securely fastening together components in space. For instance, the axial assembly configuration illustrated in
The disc sections may be assembled using a variety of mechanisms, such as clamps, coupling brackets, magnetic couplers, and/or mechanical latches (not shown). Each disc section may be formed of known space-worthy materials using techniques known in the art. However, each disc section is configured to securely contain a portion of the overall reactor system in a manner that prevents any single disc section from nuclear reactions without being properly coupled with at least one other disc section. Mechanical and/or electrical safety systems may be implemented on one or more disc sections to prevent unwanted fission reactions from occurring, either during transport of a disc section or of the assembled reactor. The assembly of the disc sections into a complete reactor may be performed, for example, using an external robotic assembly (as will be discussed below) or integrated or internal components provided with one or more of the disc sections, such as robotic arms, propulsion systems, navigation and rendezvous systems, remote control systems, and proximity operations systems. Reactor 120 may include additional features such as, not limited to, a containment shell or bracket to help contain or lock together the assembled disc sections.
It is noted that, rather than fissile fuels, the modular space reactor of
Again, the various components of the overall reactor may be split among multiple cylindrical sections or multiple components may be contained within a single section, provided the components contained within the single section are not sufficiently reactive to produce a fission chain reaction. While the radial assembly of the cylindrical sections, as shown in
Each fuel tank is designed such that a single fuel tank is not capable of sustaining a fission chain reaction under a variety of plausible scenarios or launch accident. The fluid fuel may be delivered and transferred to reactor housing and control system 412 in space. When the reactor contains enough fuel, it can go critical. In embodiments, the fluid fuel may not be solid when launched, then be converted into a fluid form when transferred to the reactor vessel in space. In some cases, the fluid fuel may be melted or vaporized prior to transfer. Each fuel tank may be sized such that a single fuel tank cannot go critical on its own under a variety of anticipated conditions.
While two fuel tanks are shown in
Similarly,
As shown in
When the disassembled components of rocket 604 are at a safe distance away from section 710, as shown in
It is noted that while
Process 800 then proceeds to a step 815 to fabricate the sections, then a step 820 to separately launch the sections into space. Then, the sections are assembled together to form the modular space reactor in space in a step 825, then the assembled space reactor is activated in a step 830. Step 830 may include, for example, coupling the fuel-containing sections together to provide sufficient fuel to initiate and sustain a fission chain reaction in the assembled space reactor. Process 800 terminates in an end step 840.
It is noted that the components shown in
For any of the embodiments described above, reactor or fuel portions may be launched together on a single launch vehicle in a ride-share configuration as long as care is taken to keep the portions separated such that the portions will not be allowed to come together to form an inadvertent critical mass, even in the extremely unlikely case of a launch accident. Alternatively, as discussed above, the various components such as fuel or reactor portions may be launched on separate vehicles, thus eliminating the possibility of inadvertent critical mass. In embodiments, each reactor or fuel portion may include its own propulsive bus with rendezvous and docking capability for reaching the other fuel or reactor portions. In other embodiments, some of the reactor or fuel portions may be deployed from a launch vehicle in a passive configuration to be retrieved by a vehicle already in space. For instance, the spaceborne vehicle may be one or more OTVs shown in
An additional advantage of the configurations described herein is the simplification of ground logistics prior to launch. By keeping the fuel and/or reactor sections separated on the ground prior to launch, the safety and handling requirements as well as logistics and regulatory burdens may be reduced in handling each fuel and/or reactor section. For instance, the safety requirements for nuclear regulatory commission licenses for storage, handling, and transportation may be significantly reduced, as each fuel and/or reactor section is incapable of itself reaching criticality. Therefore, keeping the fuel and/or reactor portions physically separated until assembly in space or on-orbit can greatly save time and cost of ground logistics, thus greatly increasing operational safety and efficiency on the ground.
The on-orbit assembly approach may also be applied to radioisotope sources as well as reactors. Some radioisotopes are extremely hazardous to launch due to their high radioactivity. For instance, in the case of a launch accident, the total effective dose (TED) to the general public may be unacceptably high, and currently the use of radioisotope-based systems are highly restricted. However, if the radioisotope sources are separated into smaller portions and launched separately, the maximum TED to the public may be limited even in the unlikely event of a launch accident. The various fuel and/or reactor portions may be launched in safe portions, then assembled in space in the manner described above, in certain embodiments.
The use of a modular space reactor may also facilitate the decommissioning or refueling of space-borne reactors. For instance, reactors for space vehicles may be refueled as needed in space, rather than having to be launched with sufficient fuel to last the vehicle's lifetime or the space vehicle being deemed space junk once it runs out of fuel. If a space reactor is designed in a modular fashion to be assembled and/or fueled in space, the space reactor may also be safely de-fueled or disassembled in in space for disposing spent fuel and/or replacing the fuel for continued operation.
As used herein, the recitation of “at least one of A, B and C” is intended to mean “either A, B, C or any combination of A, B and C.” The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. Each of the various elements disclosed herein may be achieved in a variety of manners. This disclosure should be understood to encompass each such variation, be it a variation of an embodiment of any apparatus embodiment, a method or process embodiment, or even merely a variation of any element of these. Particularly, it should be understood that the words for each element may be expressed by equivalent apparatus terms or method terms—even if only the function or result is the same. Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled.
As but one example, it should be understood that all action may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Regarding this last aspect, by way of example only, the disclosure of a “protrusion” should be understood to encompass disclosure of the act of “protruding”—whether explicitly discussed or not—and, conversely, were there only disclosure of the act of “protruding”, such a disclosure should be understood to encompass disclosure of a “protrusion”. Such changes and alternative terms are to be understood to be explicitly included in the description.
The present application claims the benefit of U.S. Provisional Pat. App. No. 63/321,690, filed 2022 Mar. 19 and titled “Space Reactor Systems and Methods of Use.” The above referenced application is incorporated hereby in its entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63321690 | Mar 2022 | US |
