The numbers
First-order sizing, with every assumption stated
These are estimates from a single baseline model. They show which ideas are worth pursuing; they are not a validated design. The values the sizing depends on most are flagged in assumptions.
load through the vehicle's hardpoints while braking (120 t at 2 g total)
peak ground power at the moment of capture, falling to zero over 3.06 s
energy per catch (≈ 40 kWh), including the 40 t carriage
Baseline timeline
120 t vehicle, 40 t carriage, capture at 30 m/s, 1 g net braking.
| Phase | Duration | Track used | Vehicle speed | What happens |
|---|---|---|---|---|
| 1 · Approach | ~4 s | — | 50 → 30 m/s | Landing burn trims to a steady 30 m/s |
| 2 · Carriage launch | 1.53 s | 22.9 m | 30 m/s | Carriage accelerates down at 2 g to 30 m/s |
| 3 · Match & capture | 0.50 s | 15.0 m | 30 m/s | Arms close at ≈ 0 m/s relative; engines cut |
| 4 · Regen braking | 3.06 s | 45.9 m | 30 → 0 m/s | 1 g net; energy to ground storage |
| 5 · Safed | — | ~6 m buffer | 0 | Latched; moved to launch mount |
Choosing the capture speed
Catching faster means burning less propellant to slow down, but it needs a taller track and more power. 30 m/s fits a track about the height of today's catch towers. That height is my recollection, not verified.
| Capture speed | Landing propellant saved (est.) | Track length | Peak power |
|---|---|---|---|
| 10 m/s | ~1,280 kg | 58 m | 31 MW |
| 15 m/s | ~1,470 kg | 70 m | 47 MW |
| 20 m/s | ~1,650 kg | 86 m | 63 MW |
| 30 m/s (baseline) | ~2,030 kg | 129 m | 94 MW |
| 40 m/s | ~2,400 kg | 187 m | 126 MW |
| 45 m/s | ~2,590 kg | 222 m | 141 MW |
Propellant saved = not burning off the capture speed, plus a constant 2.5 s of hover margin at ~364 kg/s. Track length includes acceleration, the match window, braking, hardpoint height and the buffer.
What the rocket carries
v1 onboard design: ~1,650 kg
Two REBCO coils (280 kg), a capacitor bank (625 kg), a methane cooling loop (190 kg), shielding (340 kg) and power switches (215 kg), all figures from the original deck. The methane cooling cannot work as specified, because methane freezes near 90.7 K (standard property data, quoted from memory).
v2 MagCatch: ~0–50 kg
Small ferritic latch inserts on the catch hardpoints the vehicle already has (estimate). The stainless hull is austenitic and non-magnetic, so the inserts give the electro-permanent latches something to grip.
Can the magnets help the launch?
A little. Pushing a full stack of ~5,000 t up the track (a figure from my recollection, not verified) gains only a small fraction of the speed needed for orbit.
| Added push | Track length | Extra Δv | Energy |
|---|---|---|---|
| 10 MN | 25 m | ~5 m/s | 0.25 GJ |
| 10 MN | 100 m | ~11 m/s | 1 GJ |
| 25 MN | 100 m | ~22 m/s | 2.5 GJ |
| 50 MN | 150 m | ~45 m/s | 7.5 GJ |
The version worth studying is thrust augmentation at liftoff, which might let the stack lift off heavier than its engines alone allow. It needs a full trajectory model before any payload claim, so it is a phase-3 study.
Assumptions and what is not yet verified
| Quantity | Value used | Basis |
|---|---|---|
| Vehicle landing mass | 120 t | from v1 deck |
| Carriage mass | 40 t | assumed |
| Hardpoint height above vehicle base | 38 m | assumed |
| Raptor sea-level Isp | ~330 s | recollection — not verified |
| Full stack mass at liftoff | ~5,000 t | recollection — not verified |
| Methane triple point / REBCO critical temperature | ~90.7 K / ~92 K | property data from memory |
| Hull non-magnetic | 300-series austenitic | reported alloy on modified 304L base |
| Capture gate | ±0.5 m/s, ±0.3 m | proposed target |
Failure modes
Design goal: any single failure ends in a slower stop or a wave-off, not a crash.
| Failure | Mitigation |
|---|---|
| Power lost mid-brake | Passive Halbach eddy brakes and the end-of-track buffer stop the carriage |
| Capture gate not met | Arms stay open; vehicle waves off with engines running |
| One arm fails to latch | Interlock: braking only on a confirmed dual latch, otherwise release and wave off |
| Engine fails to shut down | Brake rated for residual thrust |
| Carriage controller fault | Independent speed monitor trips to passive-brake-only mode |
Validation roadmap
Desk study
Trajectory and payload model, hardpoint loads, capture-gate simulation.
Subscale drop
~1 t article in a ~10 m shaft: eddy brake, regen motor, latch.
Rendezvous demo
A powered hopper matched to a moving carriage.
Full-scale track
Ballistic dummy, then a flight article; launch-assist study.
Operations
Cadence, turnaround and maintenance data.
Full detail in the technical deck
Every number above, with diagrams, charts and speaker notes.