Tunnel Frame

TL;DR

  • Purpose: Load-bearing structure for the Mass Driver
  • Material: Fe-6%Mn steel (strength + low temperature performance)
  • Mass: ~270 t (base 1 km)*
  • Construction: Truss frame + sulfur-concrete supports

*With extension: 2 km (~535 t), 3 km (~800 t).

Overview

The tunnel frame is a load-bearing structure that supports the rails, coils, and electronics of the Mass Driver. The frame must withstand enormous loads during acceleration (1275g).

Frame Design (Base 1 km)

Parameter Value
Length 1 km (base)*
Width 5 m
Height 4 m
Material Fe-6%Mn steel
Structure type Truss frame

*Optional: 2 km or 3 km.

Frame mass: ~270 t (1 km), ~535 t (2 km), ~800 t (3 km).

Truss Diagram (side view)

     5 m
  +------+
  | /\/\ |
  |/    \|  4 m
  |\    /|
  | \/\/ |
  +------+

Advantages of truss construction: - Lightweight (minimal material) - Strong (load distribution) - Thermally stable (no deformation at -180C)

Material: Fe-6%Mn Steel

Why manganese steel?

Property Fe-6%Mn Regular steel
Strength at -180C High Brittle
Impact toughness Retained Decreases
Cost Local production Local

Details: Iron Production

Frame Manufacturing

Production Process

Stage Equipment Output
Melting Fe + 6% Mn MRE + distillation Steel melt
Casting billets CCM-Fe 100x100 mm billets
Rolling to profile Rolling mill I-beam, channel
Cutting to pieces Gas cutting 6-12 m beams
Welding trusses WAAM + robots 12 m trusses
Anti-corrosion coating Al spraying Protection

Details: Rolling Mill, WAAM

Material Balance

Per 1 Mass Driver (1 km, ~270 t frame):

Component Mass Production
Fe-6%Mn steel (main beams) 230 t 11 t/day → 21 days
Fasteners, bolts 20 t 11 t/day → 2 days
Anti-corrosion coating (Al) 20 t 42 t/day → 0.5 day

TOTAL: ~21-25 days for material production.

With extension to 3 km: ~40-45 days.

Support Types

Sulfur-Concrete Supports (on ground)

Parameter Value
Number of supports 100 (every 10 m)*
Mass per support ~1 t sulfur-concrete
Foundation depth 2-3 m into regolith
TOTAL sulfur-concrete ~100 t

*With extension: 200 supports (2 km), 300 supports (3 km).

Sulfur-concrete on Mercury: - Binder: sulfur (S) — melts at 115°C, solidifies. Source: Titanium Line (~18 t/day) - Aggregate: regolith - No water required (unlike regular concrete) - Strength: sufficient for supports

Anchor Bolts

Parameter Value
Bolts per support 4 pcs
Diameter 20 mm
Length 1 m
TOTAL bolts 400 pcs*

*With extension: 800 (2 km), 1200 (3 km).

Frame Assembly

Sequence (base 1 km)

Stage Time Robots
Trench excavation (1 km) 2 weeks 20 Moles
Installing sulfur-concrete supports 1 week 10 Centaurs
Truss mounting (~85 sections) 1 week 20 Centaurs
Joint welding 3 days 10 Centaurs
Geometry calibration 2 days Automated

TOTAL: ~1 month from start to completed frame. (Runs in parallel with rail and coil production.)

With extension to 3 km: ~4-5 months.

Frame Loads

Static Loads (1 km)

Component Mass Load on frame
Rails (2 pcs) ~70 t 0.07 t/m
Coils (1000 pcs) ~100 t 0.1 t/m
Electronics ~3 t 0.003 t/m
TOTAL ~173 t ~0.17 t/m

Dynamic Loads

Source Force Time
Projectile acceleration (1275g) 1.44 MN per carriage 0.4 sec
Magnetic field ~10 kN per coil Impulse
Vibrations ~5 kN Continuous

Safety factor: frame designed for 3x loads. High acceleration (1275g) is compensated by short duration (0.4 sec).

Thermal Stability

Temperature Regimes

Zone Temperature Steel expansion
Shadow (main section) -180C Contraction -0.3%
Terminator (transition) 0C Neutral
Sunlit (electronics) +50C Expansion +0.1%

Compensation: - Thermal joints every 100 m - Sliding supports (allow expansion) - Pre-tension (compensates contraction)

Wear and Maintenance

Wearing Parts

Component Service life Replacement
Fastening bolts 5-10 years On schedule
Weld seams 10-20 years Ultrasonic testing
Anti-corrosion coating 3-5 years Re-spraying

Maintenance: - Monthly inspection (Centaurs + cameras) - Annual geometry calibration (laser measurements) - Replacement of worn elements as needed

Quality Control

Parameter Control Standard Action on deviation
Straightness Laser sensor (import) +/-5 mm per 100 m Support adjustment
Perpendicularity Laser sensor +/-0.1 deg Correction
Weld seams Visual (cameras) + load test No visible defects Re-welding
Bolted connections Torque wrench (local production) Torque 300 Nm Retightening

See Also