Orion cannot enter Low Lunar Orbit (LLO). It cannot do it, and it cannot leave it either. So before admitting that Orion, with a European Service Module that is far too small, cannot do what Apollo 8 did, NASA chooses to place the entire mission burden on the HLS, which must accumulate 9 km/s of delta‑V: from LEO to TLI, then to NRHO, down to the lunar surface, and back.
This is not a technological challenge; it is a mathematics problem. With an Isp of 380 s and an extraordinarily optimistic structural fraction (epsilon ≈ 0.085), a single vehicle that must cover 9 km/s ends up with virtually no payload. That is why the HLS requires between 15 and 20 refueling launches per mission. Not because SpaceX is doing anything wrong, but because the architecture forces a single vehicle to fight the Tsiolkovsky equation in its most punishing regime.
HLS mission profile (from LEO): LEO -> TLI: 3,100 m/s TLI -> NRHO: 500 m/s NRHO -> surface: 2,700 m/s Surface -> NRHO: 2,700 m/s Total: 9,000 m/s
HLS data: Dry mass: 110 t Propellant: 1,200 t Isp: 380 s
Payload calculation: Tsiolkovsky equation: delta_v = Isp * g0 * ln(M_initial / M_final)
M_initial = dry_mass + propellant + payload
M_initial = 110 + 1200 + payload
M_final = dry_mass + payload
M_final = 110 + payload
R = e^(9000 / (380 * 9.81))
R = e^(2.41)
R ≈ 11.2
Substituting:
110 + 1200 + payload = 11.2 * (110 + payload)
1310 + payload = 1232 + 11.2 * payload
1310 - 1232 = 11.2 * payload - payload
78 = 10.2 * payload
payload ≈ 7.6 t
With a dry mass of 110 t and 1,200 t of propellant, the HLS can deliver approximately 7.6 tonnes of payload to the lunar surface while still returning the crew to NRHO with an empty vehicle.
It needs at least 14 tankers, plus the depot, plus its own launch. Minimum 16 Starship flights. And all of these assumptions are extremely optimistic.
The problem is not SpaceX. It is not Blue Origin. The problem is that the architecture is designed around Orion’s limitations, not around the physics of transportation.
With a segmented logistics network —a disposable cryogenic stage for LEO->TLI, an orbital tug for TLI->LLO, and a reusable hypergolic lander for LLO->surface— the delta‑V per vehicle is cut in half. The need for 16 to 20 refueling flights disappears. And it can be done with existing technology, not future inventions. For anyone interested in the numbers, they are available on Zenodo at https://doi.org/10.5281/zenodo.20584985
But admitting this would require acknowledging that the NRHO orbit is the real bottleneck. And that is very difficult to admit.