New Mars Forums

The Perseverance rover's power source is a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), essentially a nuclear battery using heat from plutonium-238 decay to generate steady electricity (around 110 watts) and heat for its systems on Mars, providing reliable power for its long mission unlike solar panels. Provided by the U.S. Department of Energy, this compact device uses the Seebeck effect with thermocouples, offering dependable power for years in the cold Martian environment, crucial for science and operations.
How it Works:
Heat Source: The MMRTG contains plutonium-238 dioxide, a ceramic material that releases heat as it naturally decays.
Conversion: Thermoelectric couples (semiconductors) convert this heat directly into electrical current through the Seebeck effect, creating a temperature difference.
Electricity & Heat: The system produces both electricity for the rover and heat to keep its instruments and systems warm in extreme cold.
Reliability: With no moving parts, MMRTGs are highly reliable and provide continuous power for extended missions, essential for deep space and Mars exploration.
Key Features:
Power Output: Starts at about 110 watts and gradually decreases over time as the plutonium decays.
Fuel: Uses plutonium-238, a robust and long-lasting radioisotope.
Heat Management: Has "fins" to radiate excess heat and also provides warmth for the rover.
Provider: Supplied to NASA by the U.S. Department of Energy (DOE).
Why it's Used:
Provides consistent, long-term power, independent of sunlight, making it ideal for Mars exploration.
Compact and durable for space travel.
Enables long-duration missions and complex scientific operations far from the Sun

While the total Perseverance rover mission cost around $2.7 billion, the specific Radioisotope Thermoelectric Generator (RTG) powering it isn't itemized in the overall budget, but similar NASA RTGs cost roughly $100 million each, requiring plutonium and years of production, with Perseverance using about 10.6 pounds of plutonium for its.
RTG Specifics
Cost: While not a separate line item, similar NASA RTGs cost around $100 million to produce.
Plutonium Content: The system on Perseverance uses about 10.6 pounds of plutonium-238.
Production: RTGs are complex systems built at national labs (Oak Ridge, Los Alamos) and assembled at Idaho National Laboratory (INL) over years, involving robotic assembly and rigorous testing.
Perseverance Rover Total Cost Breakdown
Total Mission: ~$2.7 billion (including inflation, closer to $2.9 billion).
Spacecraft Development: ~$2.2 billion.
Launch Services: ~$243 million.
Operations (2-yr prime): ~$200-300 million.
So, while the RTG is a critical component, its significant cost is bundled into the overall spacecraft development, with estimates placing it around $100 million for the power system alone.

The MMRTG cost an estimated US$109,000,000 to produce and deploy, and US$83,000,000 to research and develop. For comparison the production and deployment of the GPHS-RTG was approximately US$118,000,000.

One standout moment came when NASA reported that Perseverance used its navigation cameras to complete a single drive of exactly 1,350.7 feet, or 411.7 meters, a stretch that set a new personal best for the rover and highlighted how efficiently it can now move across Jezero’s surface. That feat, documented in a mission update on 1,350.7 and 411.7 meters of progress, was not just a stunt; it demonstrated that the rover’s autonomous systems can safely handle long, continuous traverses that are essential for any bid at a distance record.

Recent mission commentary notes that the rover’s six wheels have already carried it roughly 25 miles, or about 40 kilometers, since touchdown, a figure that puts Perseverance in direct contention with the longest-ranging Mars rovers of the past. That cumulative distance, cited in a discussion of how far the rover has gone at around 40 kilometers, reflects not only the rover’s mechanical durability but also the mission team’s willingness to keep pushing the envelope on daily drive plans.

Astronauts can approach an operating Radioisotope Thermoelectric Generator (RTG) very closely, even working in its immediate proximity, but the exact safe distance is determined by mission design, the specific RTG's shielding, and the total duration of exposure, as part of strict radiation safety protocols.
Safety limits are based on the principle of keeping exposure As Low As Reasonably Achievable (ALARA) and not exceeding established dose limits.
Key Safety Principles
Distance is a Primary Shield: Radiation exposure decreases significantly with distance. Doubling the distance from a source can reduce the exposure rate by a factor of four (inverse square law).
Mission-Specific Limits: NASA sets specific limits for radiation exposure from nuclear technologies, which are typically capped at an effective dose of 20 millisieverts (mSv) per mission year (prorated for mission duration). This limit is designed not to add more than 10% to the unavoidable background space radiation dose of a mission.
Shielding: RTGs used in space missions are designed with shielding to minimize external radiation. For planetary surface operations (like on Mars or the Moon), the mission plan factors in habitat shielding, terrain as a potential shield, the distance from the source, and the duration of extravehicular activities (EVAs).
Time: The duration of exposure is strictly managed to stay within short-term and career dose limits.
Practical Application
In practice, astronauts on Apollo missions worked near the deployed RTGs of the Apollo Lunar Surface Experiments Package (ALSEP). They would align the ALSEP so that the RTG's cable exit pointed toward the central station, and while they avoided unnecessary proximity, no specific maximum distance constraint was imposed in the same way as avoiding a rocket launch, due to the contained nature and shielding of the RTG's radioactive material.
For future missions, safety zones and operational procedures are established through rigorous analysis to ensure that cumulative and acute radiation doses remain within safe, regulated limits for all crew members

The largest solid oxide electrolyzer (SOE) developed for Mars is the mission-scale SOXE stack by OxEon Energy, a 33x scaled-up version of the toaster-sized MOXIE device on NASA's Perseverance rover, designed to produce propellant for human return missions, though the MOXIE unit itself was the first SOE to operate on Mars, generating oxygen from CO2. On Earth, Bloom Energy's 4 MW Bloom Electrolyzer is the world's largest SOE system, stemming from that original NASA Mars technology.
For Mars Missions (Technology for Future Human Exploration):
MOXIE (Mars Oxygen ISRU Experiment): This small, toaster-sized SOE device on the Perseverance rover successfully demonstrated solid oxide electrolysis on Mars, producing oxygen from the thin CO2 atmosphere.
OxEon Mission-Scale SOXE: OxEon scaled up its MOXIE technology significantly (33x) for potential Mars crewed missions, aiming to produce large quantities of oxygen for propellant (Mars Ascent Vehicle) and life support, according to this TTU DSpace Repository document and OxEon Energy's website.
For Earth (Current Largest SOE):
4 MW Bloom Electrolyzer: Bloom Energy built the world's largest solid oxide system, operating at NASA's Ames Research Center, with roots in the original Mars technology to produce clean hydrogen for terrestrial decarbonization.
In summary, MOXIE was the first SOE on Mars, OxEon scaled it up for future large-scale Mars needs, and Bloom Energy created the largest SOE on Earth based on that heritage

The KRUSTY (Kilopower Reactor Using Stirling TechnologY) reactor operated at a target core temperature of around 800°C (1472°F), reaching up to 880°C during testing, to generate about 4-5.5 kW of thermal power for space applications, demonstrating efficient fission power at relatively high temperatures for long-duration missions.
Key Temperatures & Operations:
Design Goal: Achieve steady-state operation at ~800°C (4 kW thermal).
Peak Test Temperature: Reached up to 880°C (1616°F) during the full-power run.
Warm Criticals: Pre-test experiments heated the core to 200°C, 300°C, and 450°C to study reactivity.
Control: Temperatures were adjusted by moving control rods, allowing for standby heat or shutdown.
Significance:
Demonstrated the Kilopower system's ability to operate reliably at high temperatures, crucial for space power.
Validated nuclear codes and material performance for potential long-term use in space

MOXIE converts Martian CO2 into oxygen (O2) and carbon monoxide (CO) using solid oxide electrolysis, where roughly 2 moles of CO2 yield

1 mole of O2, meaning for every ~44 grams of CO2 consumed, MOXIE produces ~32 grams of O2, though its actual output is ~6-10 grams O2/hour from ~55 grams CO2/hour, with CO as a byproduct, not just pure O2 output. 

MOXIE's Process & Ratios: Input: MOXIE takes in Martian atmosphere (95% CO2).Reaction: It uses electrolysis to split CO2 into Carbon Monoxide (CO) and Oxygen (O).

Output: Oxygen gas (O2) is collected, and Carbon Monoxide (CO) is released as a byproduct.

Stoichiometry: The balanced equation is roughly \(2CO_{2}\rightarrow 2CO+O_{2}\) (simplified for mass flow). 

Mass Conversion (Theoretical): Molar Mass of \(CO_{2}\approx 44\) g/molMolar Mass of \(O_{2}\approx 32\) g/molFor every 44g of CO2, you get 32g of O2 (and 28g of CO).

This means for every 1 gram of O2 produced, about 1.375 grams of CO2 are needed (44/32). 

MOXIE's Actual Performance: MOXIE aims for 6 grams of O2 per hour using about 55 grams of CO2 per hour.

This 55g CO2/hour input yields ~6g O2/hour output, which is roughly a 9:1 mass ratio of CO2 in to O2 out, reflecting the byproduct CO and operational inefficiencies. 

In summary, it's not a direct 1:1 mass conversion; a larger mass of CO2 is consumed to produce a smaller mass of pure oxygen, with the rest becoming carbon monoxide

One cubic meter of Mars \(\text{CO}_{2}\) (assuming the general Martian atmosphere which is predominantly \(\text{CO}_{2}\) gas) is approximately 19 grams (0.019 kg), though the exact value varies with location and season on Mars. 

NASA's MOXIE experiment on the Perseverance rover produces oxygen by electrolyzing Martian CO2, with a typical run taking about 3.5 hours (2.5 hours warmup, 1 hour production) to generate roughly 6-10 grams per hour, enough for a small dog to breathe, exceeding initial goals by generating higher purity oxygen and scaling up production, proving technology for future human missions.

MOXIE Run Cycle Breakdown
Warmup: About 2.5 hours for the Solid Oxide Electrolyzer (SOXE) to reach ~800°C.
Production: Around 1 hour of active oxygen generation.
Total Cycle: Roughly 3.5 hours.

Production Output & Goals
Rate: 6-10 grams of oxygen per hour (g/h) in its standard runs, later reaching up to 12 g/h.
Purity: Achieved high purity (98% or better).
Total: Generated over 122 grams by its mission's end.
Analogy: 6 g/h is like a modest Earth tree; 100 minutes of oxygen is enough for one astronaut for a short time.

Key Achievements
Demonstrated oxygen production in various conditions (day/night, seasons).
Proved the viability of In-Situ Resource Utilization (ISRU) for human exploration.
Exceeded initial goals for production rate and purity, paving the way for scaled-up versions for future missions

For in situ (on-site) brick mortar on Mars, scientists developed StarCrete, a strong, starch-based biocomposite using Martian dust (regolith) and potato starch as a binder, mixed with a little salt for enhanced strength, creating materials stronger than Earth concrete, ideal for building habitats with minimal imported materials. This method uses local resources (dust, starch from food) for cost-effective, sustainable construction, producing bricks that can be made in a microwave at home-baking temperatures.
How StarCrete Works
Ingredients: Martian regolith (simulated dust), potato starch, and salt (like magnesium chloride found on Mars).
Process: Mix the starch and salt with the regolith to form a gelatinous binder, then compress into molds and heat (like in a microwave) to create strong bricks.
Strength: Martian StarCrete boasts compressive strengths of about 72 MPa, more than double ordinary concrete (around 32 MPa).
Key Advantages
In-Situ Resource Utilization (ISRU): Uses readily available Martian dust and starch from food, drastically cutting down on expensive Earth launches.
Simplicity: Can be produced with relatively low energy (home baking temperatures), unlike traditional concrete.
Resourcefulness: Starch is a food source, making it a practical, dual-purpose material.
Alternative Binders: While starch works well, researchers also explored human waste (urea from urine/sweat) as a binder, showing high strength but with potential practicality issues compared to starch.
Application for Mars
This "cosmic concrete" provides a pathway to build essential infrastructure—habitats, roads, shelters—using what's already on Mars, making long-term colonization more feasible and sustainable

When tested, StarCrete had a compressive strength of 72 Megapascals (MPa), which is over twice as strong as the 32 MPa seen in ordinary concrete.

StarCrete made from the lunar dust was even stronger at over 91 MPa.

The researchers calculated that a sack (25 Kg) of dehydrated potatoes (crisps) contain enough starch to produce almost half a ton of StarCrete, which is equivalent to over 213 brick’s worth of material. For comparison, a 3-bedroom house takes roughly 7,500 bricks to build.

Additionally, they discovered that a common salt, magnesium chloride, obtainable from the Martian surface or from the tears of astronauts, significantly improved the strength of StarCrete.

The next stages of this project are to translate StarCrete from the lab to application.

The concept of 3-axis interlocking bricks for building structures like parabolic domes on Mars is an active area of research within extraterrestrial construction, focusing on using local resources (regolith) and robotic assembly.
Key Research & Design Concepts
Interlocking Design: The primary goal of interlocking bricks is to create strong, form-fitting, and compression-dominated structures without relying heavily on traditional Earth-based mortars or adhesives, which are problematic in Mars's thin atmosphere. The wedging action of correctly shaped blocks provides stability.
3-Way Interlocking Units: Architectural and engineering research has explored using "3-way interlocking units" or "universal joints" to map non-planar, complex geometries like hemispherical or parabolic domes. These designs maximize surface contact and prevent horizontal movement, often involving complex computational design (CAD) and robotic fabrication processes (like multi-axis CNC or 3D printing with robotic arms) to achieve the precise, varied angles required for a curved surface.
Material Sourcing (ISRU): To minimize materials shipped from Earth, researchers use Martian regolith simulants to create "space bricks". Methods include:
Compression: Applying high pressure to iron-oxide-rich Martian simulant causes the nanoparticles to bind, forming solid bricks without any additional binders.
Biopolymers: Using synthetic living materials (like cyanobacteria and fungi) to "glue" regolith particles together into building blocks.
3D Printing/Sintering: Using high-powered lasers or a binding agent (such as sulfur cement) to fuse regolith layers, often employing 3-axis or 4-axis Cartesian robots to print specific material paths.
Specific Project Examples
TESSERAE Tiles: Research at MIT has focused on self-assembling tiles called TESSERAE, which use embedded magnets and specifically beveled faces to automatically assemble into complex shapes, such as a "buckyball" or dome structure, in microgravity or a controlled environment.
NASA 3D Printed Habitats: NASA has sponsored competitions and research into large-scale additive manufacturing (3D printing) of entire habitats using Martian regolith materials, often resulting in dome or vault designs (e.g., the Mars Dune Alpha habitat).
The creation of actual physical 3-axis interlocking "pieces" is generally part of specialized academic research and robotic fabrication workflows, not commercially available products in the traditional sense, as the geometry is highly specific to the intended dome's exact curvature and size