3.1.4 Titanium Line

Overview

Parameter Value
Input Magnetic fraction (ilmenite FeTiO₃ + troilite FeS)
Output TiO₂, S, Fe₂O₃
Throughput ~33 t/day
Purpose Mirror electrochromics

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Line Purpose

Extraction of TiO₂ for mirror electrochromics. Titanium (<1% in Mercury’s crust) is found in ilmenite (FeTiO₃) — a weakly magnetic mineral.

Parameter Value
TiO₂ requirement 1 kg × 600 mirrors = 0.6 t/day
Available (Ti <1%) ~4.5 t TiO₂ from 270 t regolith
Reserve ×7.5 (surplus)

Process Diagram

flowchart TD
    subgraph INPUT["MAGNETIC FRACTION"]
        MF[/"Ilmenite + Troilite<br/>33 t/day"/]
    end

    subgraph SUBLIMATION["SULFUR SUBLIMATION"]
        MF --> TS["Heating to 450°C<br/>(in vacuum)"]
        TS -->|"S↗"| S_COND["Condenser"]
        S_COND --> S_OUT[/"Sulfur<br/>~18 t/day"/]
    end

    subgraph ROASTING["OXIDATIVE ROASTING"]
        TS -->|"FeS → FeO"| OX["Roasting 900°C<br/>+ O₂"]
        OX --> FeTi["FeO + TiO₂"]
    end

    subgraph SEPARATION["MAGNETIC SEPARATION"]
        FeTi --> SEP["Magnetic<br/>separator"]
        SEP -->|"magnetic"| FE_OUT[/"Fe₂O₃<br/>→ MRE"/]
        SEP -->|"non-magnetic"| TI_OUT[/"TiO₂<br/>→ electrochromics"/]
    end

    style SUBLIMATION fill:#fff3cd
    style ROASTING fill:#f8d7da
    style SEPARATION fill:#d4edda

Stage Description Temperature
Sulfur sublimation Heating magnetic fraction in vacuum 450°C
Oxidative roasting Oxidation FeS → Fe₂O₃ 900°C
Magnetic separation Separation of Fe₂O₃ (magnetic) and TiO₂ (non-magnetic) —

Sulfur Sublimation

Troilite (FeS) is a source of sulfur for NaS batteries.

Parameter Value
Reaction FeS → Fe + S↑ (at 450°C in vacuum)
Sulfur evaporates Condenses on cold surface
Output ~18 t sulfur/day

Sulfur condenser: - Cold surface in shadow (-150°C) - Sulfur deposits as yellow crystals - Remelting: liquid sulfur (>115°C) → to battery workshop

Note: Vacuum reduces sulfur sublimation temperature, saving energy.

Oxidative Roasting

After sulfur removal, a mixture of FeO and FeTiO₃ remains. Roasting in the presence of oxygen:

Reaction Product
2FeO + ½O₂ → Fe₂O₃ Hematite (magnetic)
2FeTiO₃ + ½O₂ → Fe₂O₃ + 2TiO₂ Hematite + rutile

Parameters:

Parameter Value
Temperature 900°C
Atmosphere O₂ (from MRE cell)
Duration 2-4 hours

Magnetic Separation Fe₂O₃/TiO₂

After roasting, the mixture is separated by a magnetic separator:

Fraction Magnetic properties Product
Fe₂O₃ (hematite) Magnetic Returns to MRE cell
TiO₂ (rutile) Non-magnetic Goes to electrochromics

Note: Fe₂O₃ is valuable feedstock, returned to the main cycle for iron extraction.

Mirror Electrochromics

TiO₂ is used to control mirror orientation in space:

Component Function
TiO₂ layer Changes reflectivity when voltage is applied
Effect Uneven light pressure → torque
Control Mirror tilting without engines or fuel

Principle: A 100×100 m mirror with electrochromic coating. When voltage is applied to one edge, reflectivity decreases → light pressure becomes uneven → the mirror slowly rotates. This allows directing reflected light to the receiver without fuel consumption.

Electrochromic layer mass: ~1 kg/mirror (out of 116 kg total mass).

Advantages of Electrochromic Control

  • No consumable fuel
  • No mechanical parts
  • Powered by solar panels
  • Service life = mirror service life

Product Output

Product Quantity Application
TiO₂ (rutile) ~3 t/day Mirror electrochromics
Sulfur (S) ~18 t/day NaS batteries
Fe₂O₃ (hematite) ~12 t/day Return to MRE → iron

Sources

  • MESSENGER Mission (2011-2015) — Mercury surface composition data
  • Electrochromic Materials — TiO₂ coating research
  • Space Mirror Control — Space mirror orientation technologies

See Also