Engineering topics
Publications and source records attributed to Steven Oleson.
Long lunar nights limit science lander lifetimes to only two weeks in most global locations unless they carry large batteries or radioisotopes. An orbiting beamed power spacecraft is another option to provide this energy, thus removing the energy storage burden on the lander while still giving it years of science operations.
Titan is unique in the outer solar system in that it is the only moon with a thick atmosphere, and the only body in the solar system outside the Earth with liquid seas on its surface. The Titanian oceans, however, are seas of liquid hydrocarbons, and the rocks on the surface are solid water ice. Like other icy Moons of the outer solar system, beneath the ice crust, Titan also has a subsurface ocean. Rodriguez et al. refer to it as the “world with two oceans”, an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. [1] Titan is scientifically fascinating in many ways [2], [3], [4]. The Compass Team will emphasize just one here: Titan is a high priority target for astrobiology [4] [5] [6] [7] [8] [9] [10] [11]. It is a world with a surface and atmosphere rich in the complex organic compounds known as tholins. A detailed understanding of the nature of these complex compounds will require an analysis using a full laboratory on Earth. Because of its value to understanding the organic compounds of the outer solar system which may be the primordial building-blocks of life, return of samples from Titan to laboratories on Earth will be the primary goal of this mission. While this would give unprecedented science return, returning even a small sample from Titan using conventional technology would be tremendously difficult. Saturn is almost a billion miles from the Earth, about thirteen times farther than Mars. A return mission to Saturn requires such a large total-mission ∆V that, with conventional technology, the mass ratios required are prohibitive. Such a sample return would truly be “mission incredible.” But to date, a sample return mission from so distant a target has been assumed to be, not merely incredible, but mission impossible. The Compass Team has proposed [2] [12] that by manufacturing the propellant for the return to Earth using the resources available on Titan, such a mission becomes possible. The task of this report is to show that it is reasonable with credible space technology.
Compass Team was tasked by the RPS Project at the NASA Glenn Research Center (GRC) to create an independent concept design for a spacecraft (S/C) utilizing low power radioisotope power. A list of candidate missions enabled by milliwatt class radioisotope power was evaluated and thus resulted in the selection of a Mars polar region seismology network of four hard landers. A science rational and science operations plan was developed to establish mission design requirements and S/C subsystem concept designs described herein.
Continuous power at the kilowatt level will be imperative for future lunar users including crew infrastructure, future science, and in-situ resource utilization (ISRU). The Compass Team explored both 10 kilowatt electric (kWe) and 40 kWe concepts, assuming planned lander and rover capabilities. Both concepts found that a crew pressurized rover chassis, repurposed for deploying reactor power components, could place a fission surface power system (FSPS) at least one kilometer from users. While the 10 kWe fission power system (FPS) could be deployed as a single unit, the 40 kWe system was too large and had to be deployed in multiple trips with the same rover. Key technologies and design approaches included a high-assay low-enriched uranium (HALEU), yttrium hydride (YH) moderated heat pipe reactor, Stirling convertors, deployable radiators based on International Space Station (ISS) designs, and power conversion/transmission at ±2800 volts of direct current (VDC).
The Radioisotope Power Systems (RPS) Program tasked the Compass Team to evaluate use of Dynamic Radioisotope Power Systems (DRPS) for lunar science rovers. The object was to identify their advantages and challenges as well as to influence the technology developments with flight-type requirements. This was easily done by using the promising Volatiles Investigating Polar Exploration Rover (VIPER) solar- powered rover mission as a platform to ‘swap in’ a DRPS. The ‘pickup truck bed’ approach allowed both simplified installation and operation of the DRPS while keeping the forward lunar surface ‘blocked’ from the DRPS waste heat which could sublimate the icy surface. It was found that with the Stirling DRPS option the mass is within the planned VIPER lander capability and is very close to VIPER mass and size (the DRPS replaces large battery pack/solar arrays). The Stirling DRPS option produced ~300 Watts electrical (We) using six general purpose heat source (GPHS) bricks and eight Stirling convertors. Replacing the solar/battery power with radioisotope power allows a continuous presence (instead of 6 hours) in a permanently shadowed region (PSR) and over 18 months of operations with minimal science impact (rearward surface heating). It was also found that use of a dynamic system (instead of a thermoelectric system) reduces the heat impact on the science environment two-to-three times. The DRPS, along with a relay link (like Gateway), can provide continuous access to PSRs. The system was also found to be capable of roving for 8 hours per day with a range of over 500 km in 18 months. Preliminary cost estimates fit into a Class D mission but only assuming VIPER heritage and launch, lander, operations, nuclear specific costs [National Environmental Policy Act (NEPA), fueling, transport, Launch Services Program (LSP), etc.] and DRPS are not included.
To enable future human exploration missions, the lunar surface will serve as a crucial training ground and technology demonstration test site where NASA will prepare for future human missions to Mars and other destinations. Key enablers in this exploration are rover systems intended to operate in both the lunar and Mars surface environments. This study focused primarily on the Mars surface environment because, compared to the near-continuous illumination near the lunar poles, the day/night cycles and the reduced solar illumination on Mars make it much more difficult to use solar power. However, solar power is not the only power generation technology available. Top-level energy studies have shown that a radioisotope power system (RPS) has promise for supplying both power and thermal energy for crewed rovers on both the Moon and Mars. This design study investigates how an RPS could potentially meet the power and thermal needs of a pressurized rover with applications for both destinations. The design focus is on what service an RPS can provide and how it would be integrated into a rover (power and thermal interfaces, placement, radiation shielding, fairing installation on the pad, etc.).
The Compass team developed three designs for a soft lander for the International Lunar Network (ILN) using different power systems. These systems included solar arrays and batteries and two radioisotope power system (RPS) options scaled down from previous designs. These are a half Stirling radioisotope generator and a one-eighth Radioisotope Thermoelectric Generator (RTG). The COMPASS design consists of a soft-lander capable of network science (seismic, magnetospheric, laser reflector, and thermal transfer) that can land anywhere on the near side of the Moon and operate for at least six years. The baseline version, using only batteries and solar arrays, requires a very large battery (~80 kg) for the roughly 20 W night-time power requirements. The lander launch mass (with solid rocket breaking motor) is almost 900 kg. With such a large battery, the lander will require a launcher larger than the desired Minotaur V; a Taurus II (being developed for NASA Commercial Orbital Transportation Services (COTS)) or larger (Delta II or Atlas V) would be needed. The two RPS cases, half an Advanced Stirling Radioisotope Generators (ASRG) and one-eighth RTG have much smaller launch masses of 500 and 600 kg respectively. (The one-eighth RTG case lacks the power for the full science package, so a solar array battery is still needed.) Unfortunately, the Minotaur V’s launch capability is still not large enough (~430 kg to trans-lunar injection (TLI)) for the RPS systems. Consequently, a fourth case was developed to fly a limited science floor suite of instruments (seismometer only) which reduced the RPS Lander launch mass to fit on a Minotaur V.
This conceptual design study investigated trading several Dynamic Radioisotope Power Systems (DRPS) in development to supply power to a lunar science rover which operates for long periods (months) in permanently shadowed regions (PSR) over many years. The design was conducted by the Compass team and relied heavily on the planned VIPER rover design, which is limited to only a few hours of operations in PSRs and less than a month near the south pole. As such this conceptual design shows what a DRPS can do for a follow-on type VIPER rover. In addition to the long duration, go anywhere DRPS power system, the Compass team added a communications system that utilizes the Gateway spacecraft as a relay node for nearly 24/7 communications link to the DRPS rover in lunar craters not visible from the earth. The Compass design includes a notional conops, launch and delivery, subsystem designs of power, mobility, structures, science, command and data handling, communications, guidance and control, and thermal. The thermal design was especially important due the low temperatures in PSRs where the science environment needs to be shielded from the waste heat from the DRPS.
This paper is a retrospective of the lessons learned during the almost 15-year history of the Compass concurrent mission and systems design team at NASA’s Glenn Research Center (GRC). It examines the key factors in the team’s evolution from a temporary group gathered to perform a single study to the successful, sustainable team it is today. Compass is a matrixed team of experts with various technical backgrounds and personalities. They collaborate over a two-week period either physically in a dedicated meeting space, or virtually to design a space system (Spacecraft, stage, science package, etc). Over the years, because of the rapid nature of the design studies, the team leadership has iterated on the optimal team member personality makeup, facility elements and tools as well as NASA GRC management support necessary to lead to sustained success.
We propose a “magneto-inductive” technology, employing a sensitive receiver based on a Superconducting Quantum Interference Device (SQUID), to enable communications through conductive media, so as to pave the way for exploration of ocean worlds, especially a Europa scenario. Concepts for ice penetration systems to access the presumed liquid ocean on Europa are under development but it was previously considered impractical if not impossible to communicate through the briny ice with conventional propagating electromagnetic signals.
Under the Mars Transportation Assessment Study, NASA and DOE are performing analyses and generating concepts for crewed Nuclear Electric Propulsion (NEP) missions to Mars. This paper presents the results of trade studies and concept development for the nuclear electric power system, consisting of the fission reactor, radiation shielding, power conversion, heat rejection and power management & distribution (PMAD). The nuclear power team completed trade studies to evaluate different reactor and power conversion technologies and developed preliminary concepts for the crew shielding, waste heat radiators, and PMAD. The initial results suggest that a modified terrestrial microreactor combined with supercritical CO2 Brayton conversion could be used to perform the crew and cargo missions with satisfactory performance and modest risk.
Status of NIAC Phase I study for NIAC Symposium (remote). An overview of the Insitu Titan Sample Return concept. The Compass team developed a concept to return 3 kg of cryogenic samples from the surface of Saturn's moon Titan by gathering ~3000 kg of ice and methane to fuel an inflatable, 3 stage launch vehicle to propel a return vehicle and aeroshell back to earth. Note: This presentation does not include voice information and is not available for this record.
The Radioisotope Power Systems (RPS) Program tasked the Compass Team to evaluate use of Dynamic Radioisotope Power Sources (DRPS) for lunar science rovers. The object was to identify their advantages and challenges as well as to influence the technology developments with flight-type requirements. This was done by using the promising Volatiles Investigating Polar Exploration Rover (VIPER) solar-powered rover mission as a platform to ‘swap in’ a DRPS. The resulting design used a ‘pickup truck bed’ approach which allowed simplified installation and operation of the DRPS while also keeping the forward lunar surface ‘blocked’ from the DRPS waste heat, which could sublimate the icy surface. It was found that with the Stirling DRPS option the mass is within the planned VIPER lander capability and is comparable to VIPER mass and size (the DRPS replaces large battery pack/solar arrays). The Stirling DRPS option produced ~300 Watts electrical (We) using six general purpose heat source (GPHS) bricks and eight Stirling convertors. Replacing the solar/battery power with radioisotope power allows a continuous presence (instead of six hours) in a permanently shadowed region (PSR) and over 18 months of operations with minimal science impact (rearward surface heating). It was also found that use of a dynamic system, instead of a thermoelectric system, reduces the heat impact on the science environment two-to-three times while still providing sufficient waste heat for the rover systems in the PSR (~ -200°C). The DRPS, along with a relay link (like Gateway), can provide extended access to PSR. The system was also found to be capable of roving for eight hours per day with a range of well over 100 km in 18 months.
Continuous power at the kilowatt level will be imperative for future lunar users including crew infrastructure, future science, and in-situ resource utilization (ISRU). The Compass Team explored both 10 kWe and 40 kWe concepts, assuming planned lander and rover capabilities. Both concepts found that a crew pressurized rover chassis, repurposed for deploying reactor power components, could place a fission surface power system (FSPS) at least one km from users. While the 10 kWe fission power system (FPS) could be deployed as a single unit, the 40 kWe system was too large and had to be deployed in multiple trips with the same rover. Key technologies and design approaches included a high-assay low-enriched uranium (HALEU), yttrium hydride (YH) moderated heat pipe reactor, Stirling convertors, deployable radiators based on International Space Station (ISS) designs, and power conversion/transmission at ±2800 VDC for a one km remote distance.
To assess ‘quick’ missions to Mars, a study was performed to determine the feasibility of a two-year roundtrip class mission concept of operation that enables boots on Mars in the 2030s. After performing a Phase 1.1 2036 Mars opposition design case, the more difficult 2039 opposition design was pursued. This Phase 1.2 also sought to further refine the concept, building on feasibility, and addressing several challenges brought by independent team reviews. Given the date of 2039, nearer-term technologies, primarily nuclear thermal and nuclear electric were deemed as the most viable for these missions. This paper explores a nuclear electric and chemical combined propulsion approach to achieve the desired mission timeline.
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Explore the source record for details and available documents.