| Physical properties | Average numerical value, MKS units |
|---|---|
| Density of magma @ 1473 K | 2600-2700 kg/m3 |
| Density of solid | 2900-2960 kg/m3 |
| Hygroscopicity | 0.1% |
| Tensile strength | 3.5×107 N/m2 |
| Compressive strength | 5.4×108 N/m2 |
| Bending strength | 4.5×107 N/m2 |
| Modulus of elasticity (Young's modulus) | 1.1×1011 N/m2 |
| Moh's hardness | 8.5 |
| Grinding hardness | 2.2×105 m2/m3 |
| Specific heat | 840 J/kg K |
| Melting point | 1400-1600 K |
| Heat of fusion | 4.2×105 J/kg(+/-30%) |
| Thermal conductivity | 0.8 W/m K |
| Linear thermal expansion coefficient | |
| ... 273-373 K | 7.7×10-6 m/m K |
| ... 273-473 K | 8.6×10-6 m/m K |
| Thermal shock resistance | 150 K |
| Surface resistivity | 1.0×1010 ohm-m |
| Internal resistivity | 1.0×109 ohm-m |
| Basalt magma viscosity | 102-105 N-sec/m2 |
| Magma surface tension | 0.27-0.35 N/m |
| Velocity of sound, in melt @ 1500 K | 2300 m/sec (compression wave) |
| Velocity of sound, solid @ 1000 K | 5700 m/sec (compression wave) |
| Resistivity of melt @ 1500 K | 1.0×10-4 ohm-m |
| Thermal conductivity, | |
| ... melt @ 1500 K | 0.4-1.3 W/m K |
| ... solid @ STP | 1.7-2.5 W/m K |
| Magnetic susceptibility | 0.1-4.0×10-8 V/kg |
| Crystal growth rate | 0.02-6×10-9 m/sec |
| Shear strength | ~108 N/m2 |
5C.2 Power Requirements for Paving Robots
To obtain a baseline design for LMF paving robots a rough estimate of the power required to fuse the basalt slabs required (in a reasonable amount of time) must be made. For this crude model, basalt platform slabs were taken as square plates with horizontal dimension x and vertical dimension y, with a sintering margin of width s (2s between slabs). A platform of radius R must be constructed within a time r, so a total of πR2/(x + s)2 slabs must be produced in 7 sec, a rate of t-1 = πR2/r(x + s)2 slab/sec.
The total input power to each square meter of lunar regolith for slab production is given by:
- P = Ph + Pm + Pr + Pc
where P is total power required, Ph is the power needed to heat the basalt material to its melting point, Pm is the power necessary to melt the slab at the melting point, Pr is the rate at which energy is lost due to radiation from the top surface of the slab, and Pc is the rate of energy loss by conduction into the lunar subsurface (modified from Davies and Simpson, 1979). Radiation losses through the thin slab side walls are ignored.
To a first approximation it is sufficient to simply calculate the total energy which must be supplied and divide this by the length of time spent on each slab, hence:
- Ph = Hs(Tm - TL)x2yp/t
- Pm = Hfx2yp/t
