Gear Ratio: Launched Mass per Ton Delivered

Definition

Launched Mass per Ton Delivered

Gear ratio = launch factor × e^{Δv / (Isp × g₀)} ÷ (1 - dry mass fraction).

The exponential is the rocket equation's mass ratio for the corridor. Dividing by one minus the dry mass fraction, 0.10 here, adds tanks and engines. The launch factor, 5.2×, is the site's Earth-to-LEO gear ratio and applies to every route that starts in LEO; routes that start off Earth use 1 and are marked local.

The Δv Corridor Calculator runs the same formula for any route, propulsion class, payload and dry fraction.

By corridor

Gear Ratio by Corridor and Propulsion Class

Every corridor in the index at four specific impulses.

Gear ratio by corridor and propulsion class
Corridor	Δv km/s	LOX/CH₄, 360 s	LOX/LH₂, 450 s	Nuclear thermal, 900 s	Nuclear electric, 3,000 s	Rated
LEO → GEO	3.90	17.4×	14.0×	9.0×	6.6×	Modeled
LEO → EML-1	3.77	16.8×	13.6×	8.9×	6.6×	Modeled
LEO → SEL-1	3.40	15.1×	12.5×	8.5×	6.5×	Modeled
LEO → SEL-2	3.40	15.1×	12.5×	8.5×	6.5×	Modeled
LEO → Lunar surface	5.90	30.7×	22.0×	11.3×	7.1×	Modeled
Lunar surface → EML-1 (local)	2.52	2.3×	2.0×	1.5×	1.2×	Modeled
Lunar surface → Lunar orbit (local)	1.87	No propellant	No propellant	No propellant	No propellant	Modeled
EML-1 → Mars transfer (local)	0.77	1.4×	1.3×	1.2×	1.1×	Modeled
LEO → Mars surface	4.90	23.1×	17.5×	10.1×	6.8×	Modeled
Phobos → Mars surface (local)	~0.9	1.4×	1.4×	1.2×	1.1×	Modeled
Deimos → Ceres (local)	~2.9	2.5×	2.1×	1.5×	1.2×	Modeled
LEO → Ceres	9.60	87.6×	50.9×	17.1×	8.0×	Modeled
LEO → Callisto	11.80	163×	83.8×	22.0×	8.6×	Modeled
LEO → Titan	12.60	205×	100×	24.1×	8.9×	Modeled
LEO → Triton	16.40	601×	238×	37.0×	10.1×	Modeled
LEO → Pluto-Charon	18.20	1,001×	357×	45.4×	10.7×	Modeled

Chemical gear ratios past Mars run into the hundreds and are why every outer-system plan assumes NEP. NEP cannot land; its column applies to in-space legs only. Propulsion detail is on Propulsion Classes.

Reading it

Below 3× Ship It; Above 10× Make It

The bands used by the calculator.

Gear ratio bands
Gear ratio	Reading	Rated
Under 3×	Shipping usually wins; local production has to beat a supply chain that already works	Modeled
3-10×	Contested: yield, capital cost and site life decide it	Modeled
Over 10×	Making it locally wins even at poor yields	Modeled

The gear ratio prices launch; it does not decide the mass test for a local plant. Plant and product travel the same corridor, so the gear ratio cancels out of the closure ratio on the Ship-or-Make Threshold. It sets what the plant saves in launch cost once the mass test passes.

China

Chinese Vehicles on the High-Ratio Corridors

The vehicles carrying Chinese payloads up the steepest gear ratios.

Chinese launch and upper stages
Vehicle	Corridor	Data point	Rated
Long March 5 · CALT	LEO → Lunar surface; LEO → Mars surface	Launched Chang'e-5 (2020) and Tianwen-1 (2020)	Observed
Long March 3B · CALT	Earth → Lunar surface	Launched Chang'e-3, Chang'e-4 and Tianwen-2	Observed
Long March 10 · CALT	Earth → Lunar surface, crewed	Two launches per crewed landing: Mengzhou and Lanyue separately	Building
Zhuque-3 · LandSpace	Earth → LEO	Stainless-steel, methane-fueled reusable booster	Building

Contested

Deliberately Not Claimed

The load-bearing uncertainties, tagged with the confidence they actually earn.

Modeled

The 5.2× launch factor is a site convention. It is carried unchanged so every page agrees. A reusable vehicle's launch factor depends on how much hardware returns, which no single number captures.

Modeled

NEP ratios use impulsive Δv. A low-thrust spiral out of Earth's gravity well costs about twice the impulsive Δv, so the NEP column understates.

Modeled

One dry fraction for every vehicle. 0.10 suits a large tank stage; landers and long-coast stages with boil-off control run higher.

Record

Provenance and Data Sources

Confidence: Observed for flown, fielded or measured - Building for hardware and programs in development - Projected for announced plans - Modeled for original analysis
Status date: Q4 2026
Method: Rocket equation, g₀ = 9.80665 m/s²; dry mass fraction 0.10; launch factor 5.2×
China: CALT Long March 3B, 5 and 10; LandSpace Zhuque-3
Weakest link: The NEP column