A technical deep-dive into humanity’s return beyond Low Earth Orbit — trajectory, orbital mechanics, and propulsion physics. Created with Claude, April 2026.
Mission Overview
Artemis II — the first crewed deep-space mission since Apollo 17 in 1972. Four astronauts aboard Orion on a free-return lunar flyby using the Space Launch System Block 1.
April 9, 2026Planned launch
~10.3 daysMission duration
252,757 miMax distance from Earth
24,500 mphPeak velocity (TLI)
8.8M lbfSLS liftoff thrust
Crew
- CDR Reid Wiseman (NASA)
- PLT Victor Glover (NASA)
- MS1 Christina Koch (NASA)
- MS2 Jeremy Hansen (CSA)
Four-Phase Trajectory
| Phase | Duration | Key Events |
|---|---|---|
| 1. Launch & Parking Orbit | T+0 to ~T+12 min | SRBs + Core Stage to LEO; 115 mi × 1,400 mi highly elliptical orbit |
| 2. Earth Orbit Checkout | ~24 hrs (1 orbit) | Systems check; proximity ops with spent ICPS stage |
| 3. Trans-Lunar Injection (TLI) | ~5 min 49 s burn | ESM burn; Δv ≈ 388 m/s; speed reaches 24,500 mph |
| 4. Lunar Flyby & Return | 4-day coast + flyby | Closest approach 4,066 mi; free-return trajectory to Earth; 40-min comms blackout behind Moon |
Propulsion Stack
| Stage | Engine | Thrust (vac) | Isp (vac) | Propellant | Purpose |
|---|---|---|---|---|---|
| SRB × 2 | RSRM-V | 3.6M lbf each | 268 s | HTPB Solid | Max-q ascent boost |
| Core Stage | RS-25 × 4 | 512,000 lbf × 4 | 452 s | LH&sub2; / LOX | Main ascent burn |
| ICPS | RL10C-2 × 1 | 24,750 lbf | 465 s | LH&sub2; / LOX | Trans-Lunar Injection |
| ESM (main) | AJ10-190 × 1 | 6,000 lbf | 316 s | MMH / NTO | OMs, trajectory corrections |
| ESM RCS | 490 N × 8 | 110 lbf each | ~280 s | MMH / NTO | Attitude & fine MCC |
The Tsiolkovsky Rocket Equation
The master equation governing all propulsive maneuvers:
Δv = Isp × g&sub0; × ln( m&sub0; / mf )
- Δv — change in velocity the burn achieves (m/s)
- Isp — specific impulse: engine efficiency (seconds)
- g&sub0; — standard gravity: 9.80665 m/s²
- m&sub0; — wet mass (dry mass + propellant)
- mf — dry mass after burn
Worked Example: ICPS TLI Burn
Engine: RL10C-2 — Isp = 465 s; ICPS wet mass m&sub0; ≈ 30,700 kg; dry mass mf ≈ 3,500 kg
ve = 465 × 9.806 = 4,560 m/s • Δv = 4,560 × ln(30,700 / 3,500) = 4,560 × 2.171 ≈ 9,900 m/s
Combined with Orion (~26,000 kg), total mission Δv ≈ 3.1–3.4 km/s.