Launch Vehicles

NEPTUNE Series Orbital Launch Vehicles

N1 rocket

About the NEPTUNE Series Orbital Launch Vehicles

Interorbital Systems' innovative NEPTUNE series modular rockets are poised to provide the world's lowest-cost access to space for orbital, Lunar, and interplanetary spacecraft. IOS modular launch vehicles are designed to reliably ferry payloads from 30-kg to 3,200-kg to Low-Earth-Orbit using its simple building block propulsion unit, the NEPTUNE Building Block (NBB).

NEPTUNE Building Block

The pressure-fed NEPTUNE Building Block is the primary propulsion module of the NEPTUNE series rockets. Each standard NEPTUNE Building Block is composed of four propellant tanks (two fuel and two oxidizer tanks), a single throttleable, ablatively-cooled, gimballed rocket engine, a valve unit, an optional roll system, and a controller. Construction costs are kept low by building the major rocket components in-house, using off-the-shelf components when necessary (for example: ball valves and micro-controller boards), and applying efficient automated mass-production methods.

NEPTUNE Nomenclature

Each two-stage NEPTUNE rocket variant consists of one or more NEPTUNE Building Blocks arranged side-by-side in parallel or stacked in tandem. The mission payload capacity is determined by the number of NEPTUNE Building Blocks used in the launch-vehicle variant. Variants are designated by their NEPTUNE Building Block count. For example, a NEPTUNE 9 Two Stage, or N9TS, is assembled from nine NEPTUNE Building Blocks. The minimum orbital flight configuration, the two-stage N2TS, has a two NEPTUNE Building Blocks stacked in tandem.

Liquid Rocket Engines and Propellants

A single, throttleable liquid rocket engine powers each NEPTUNE Building Block. Four thrust options are available for the NEPTUNE Building Block engines: 1,000, 7,500, 10,000, or 30,000 pounds of thrust (GPRE 1.0KNTA, GPRE 7.5KNTA, GPRE 10.0KNTA, or GPRE 30.0KNTA). Storable, high-density white fuming nitric acid (WFNA) and turpentine power the NEPTUNE Building Block engines. These environmentally-friendly propellants provide reliable and efficient hypergolic ignition, eliminating the need for an ignition system. Each NEPTUNE Building Block's main rocket engine is gimballed to provide pitch, yaw and roll control (multiple NBBs). For a stand-alone NEPTUNE Building Blocks (N2 variant), four cold-gas thrusters provide roll control. All IOS liquid rocket engines are ablatively cooled and are rapidly manufactured using a filament-winding process.

Learn more about NEPTUNE propellants

Pressure-fed System

NEPTUNE rocket engines are pressure-fed. IOS has eliminated the requirement for a pump by developing ultra-lightweight filament-wound propellant tanks and by utilizing high-density propellants that substantially reduce the size of the propellant tanks. The NEPTUNE pressurization system is lighter, less complex, and therefore cheaper and more reliable than equivalent pump-fed systems. Ablative-cooled and pressure-fed propulsion systems simplify the process of starting and stopping the rocket engines on the ground and in space.

Payload Capacity

Launch Vehicle Variant: Two Stage Payload Mass and Altitude
N2 Two Stage 30.0-kg (66.2-lb) to 500 km (310.0-mi) polar orbit
N9 Two Stage 1,250.0-kg (2,756.0-lb) to 500 km (310.0-mi) polar orbit
N36 Two Stage 3,200.0-kg (7,056.0-lb) to 500-km (310.0-mi) polar orbit


Structural components are manufactured using mostly composite materials and aluminum. The propellant tanks and the rocket engine chambers and nozzles are filament wound using proprietary robotic technology.


IOS uses a guidance and control system developed in-house.

Ablatively Cooled Engine

IOS rocket engines are ablatively cooled. Ablative cooling is a reliable, low cost cooling method that was chosen for the Apollo service module and LEM rocket engines. Engines with ablative cooling can be rapidly constructed, and simplify the process of starting and stopping the engines in the vacuum of space.

Exclusive Ocean-Based Launch

All IOS rockets are launched from an ocean-going barge. This eliminates the enormous cost of launching from the existing land-based spaceports and allows IOS to schedule launches based only on the weather and sea conditions.

NEPTUNE in Action

NEPTUNE Building Block Test Vehicle was launched in 2014. Its successful launch (below) marked the first launch of a NEPTUNE variant and the first flight test of the NBB rocket engine. The IOS Neutrino rocket launch in 2018 was the first test of the NBB GPRE 1.0KNTA rocket engine.

NEPTUNE Series Rockets: The Future

Renderings of N9TS and N36TS launches

Interorbital Systems is currently focused on launching smaller payloads to Low Earth Orbit (LEO) with the N2TS launch vehicle. After the completion of the N2TS development and launch program, the N9TS and N36TS variants will enter their test phase. NEPTUNE rockets can fly a variety of mission profiles - in addition to launching small and medium satellites to LEO, Lunar orbital and Soft Landing spacecraft as well as interplanetary payloads can be accommodated. The LunarStation is slated to be launched on a NEPTUNE 9 Two Stage (N9TS) rocket as early as 2021. A lunar sample return mission could be launched later that year.


Also in development is the TRITON Building Block. The TRITON 9 Two Stage (T9TS) will be a Soyuz-class launch vehicle and the TRITON 36 TS (T36TS) will be a Titan IV plus class vehicle. These will be the work horses for the planned IOS Lunar colonization effort.