This analysis approximates an electric space tug using a Turion TIE-20 GEN2 ion thruster (55 mN thrust, 4500 s ISP @ 2 kW, mass 23 kg, price \$150 k) powered by solar arrays. We evaluate three propellant choices: Xenon, Krypton, and Argon.
| Propellant | Estimated ISP (s) | Exhaust Velocity (m/s) | Price/kg (Earth retail) |
|---|---|---|---|
| Xenon | 4000 | ≈39 240 | \$4 500 |
| Krypton | 3000 | ≈29 430 | \$850 |
| Argon | 2500 | ≈24 525 | \$2.50 |
Notes: Typical specific impulse values for advanced ion/Hall thrusters vary with design and power level; xenon ~4 000 s, krypton ~3 000 s, argon ~2 500 s are representative averages for analysis. Cost estimates draw from noble gas price data. :contentReference[oaicite:0]{index=0}
We approximate the required Δv from LEO to a lunar flyby as ~3.8 km/s. Using the rocket equation:
mpropellant = mstart·(1–exp(–Δv/(Isp·g)))
| Propellant | Mass Fraction to TLI | Propellant to TLI (kg) | Propellant Return (kg) | Total Propellant Launched (kg) |
|---|---|---|---|---|
| Xenon | 0.10 | ≈111 | ≈111 | 222 |
| Krypton | 0.12 | ≈133 | ≈133 | 266 |
| Argon | 0.14 | ≈155 | ≈155 | 310 |
Assumptions: Dry mass includes the tug dry (thruster + structure + solar), payload 1000 kg. Return trip uses same Δv magnitude with no payload; propellant fraction computed similarly. These values are approximate and neglect gravity losses, finite thrust inefficiencies, and station‑keeping. For electric propulsion with high ISP, Δv requirements dominate mass fraction.
| Component | Mass (kg) | Unit Cost |
|---|---|---|
| Payload | 1000 | — |
| Thruster (Turion TIE‑20) | 23 | \$150 000 |
| Solar Arrays & Structure | 200 | \$200 000 |
| Propellant Tanks | ≈(10% of propellant) | — |
| Propellant (Xenon) | 222 | \$999 000 |
| Propellant (Krypton) | 266 | \$226 100 |
| Propellant (Argon) | 310 | \$775 |
| Scenario | Total Mass to LEO (kg) | Total Launch Cost High (\$1000/kg) | Total Launch Cost Low (\$200/kg) | Other Costs | Total Cost High | Total Cost Low | $/kg Payload |
|---|---|---|---|---|---|---|---|
| Xenon Disposable | ≈1435 | \$1 435 000 | \$287 000 | Tug \$350 000 + Xe \$999 000 | \$2 784 000 | \$1 636 000 | 2784 / 1000 ≈ 2784 |
| Xenon Reusable | ≈133 | \$133 000 | \$26 600 | Xenon \$999 000 | \$1 132 000 | \$1 025 600 | 1132 / 1000 ≈ 1132 |
| Krypton Disposable | ≈1509 | \$1 509 000 | \$302 000 | Tug \$350 000 + Kr \$226 100 | \$2 085 100 | \$878 100 | 2085 / 1000 ≈ 2085 |
| Krypton Reusable | ≈266 | \$266 000 | \$53 200 | Kr \$226 100 | \$492 100 | \$279 300 | 492 / 1000 ≈ 492 |
| Argon Disposable | ≈1581 | \$1 581 000 | \$316 200 | Tug \$350 000 + Ar \$775 | \$1 931 775 | \$667 * | 1931 / 1000 ≈ 1931 |
| Argon Reusable | ≈310 | \$310 000 | \$62 000 | Ar \$775 | \$310 775 | \$62 775 | 311 / 1000 ≈ 311 |
Assumptions & Notes: